This tutorial lists many common roof types, roughly in ascending order of complexity, and gives examples of each one.
Wikipedia provides additional information and diagrams at the following URL: http://en.wikipedia.org/wiki/List_of_roof_shapes, and from that page there are links to other articles with lots more reference images.
Please note that roof terminology is not defined with absolute rigidity. Usages vary from place to place, and from one architect or builder to another. One person may describe the alternative Mansard roof design shown on these pages as a 'bonnet roof', for example, and this is understandable given the similarities between the two roof shapes.
Roof designs also vary, so that there may be no discernible difference between a 'hipped roof with a gable end' and a 'link dormer', or between one person's 'skillion roof' and another's 'shed roof'. Every element of every roof type may be adjusted, and most roof types can be combined in different ways, producing unlimited numbers of local variants.
Historically, when people added to their homes, they tended to follow the building practices of their day. Over centuries, long-lived properties can accumulate a wide variety of different styles. Sometimes the changes are obvious, such as Rochester Castle, which has three square towers and one round, because one of the square towers was destroyed during a siege and then rebuilt as a stronger round tower. Other times, the changes may blend to produce an eccentric but charming building with its own unique mix of architectural features.
Flat roof
Blacksmith's building from the NPC village.
This roof type may also be referred to as a parapet roof, meaning a roof with a parapet (a low protective wall) around it.
Making a flat roof is trivial, but making a flat roof that looks real takes a little more effort. Take a leaf from the blacksmith's book from the NPC Village and add a border; that little extra effort greatly helps make this simple structure look more attractive.
Always try to use different block types for a roof border. Use slabs, as in the illustration, or backwards steps, forming a gutter, or add a border of blank signs all the way round the building, or a parapet, thus making the roof area safe to use. The only thing you shouldn't do is to just use the same materials as for the rest of the building.
Balcony
A partly covered balcony.
Flat roofs have a greater tendency than other roof types to leak, which means access to the flat roof may be necessary anyway. Hence it's not uncommon for flat roof sections to be paved in some way so that they are useful as outdoor living areas of some kind. Balconies may be large or small, covered or open, or a mixture of the two. Buildings may have multiple balconies on multiple levels.
Shed roof
A shed roof.
A shed or sloped roof is sloped in one direction only. This design is not commonly used for inhabited buildings, and is more likely to be seen on cheap, simple or utilitarian buildings such as sheds, animal houses, outhouses or storage barns.
Gable roof
Simple gable roof design, not suitable for buildings with widths greater than about 12 blocks.
A gable roof, also known as a pitched or peaked roof, is an inverted 'V'. This roof design is common in NPC villages and is useful for small buildings. The building in the image is 6×10 metres. Allowing for the very thick walls one gets in Minecraft that give a usable internal space of 4×8 metres; sufficient for one or two rooms. A building of this size integrates well with NPC village buildings.
Saltbox roof
A saltbox roof.
Alternative saltbox roof.
A saltbox roof is a type of gable roof where one slope is much longer than the other. Buildings with this roof type quite often have two storeys at the front and one at the back; adding a lean-to back roof to an existing structure in this manner is a simple way to extend a building. The front and back slopes of a saltbox roof may have the same pitch, but as the second picture shows this is not always the case.
Clerestory roof
A clerestory or half-monitor roof.
A clerestory is a window too high to see out of which lets light in to a building. Hence celestory roof is a generic term referring to a roof shaped to include clerestory windows. This roof shape may also be referred to as a half-monitor roof.
Hipped roof
A building with a simple hipped roof.
A pyramidal roof.
A hipped roof (or hip roof) is sloped in both directions. There is far less roof volume (for an attic) available under a hipped roof. Placed on a square building, a hipped roof produces a distinctive pyramid-shaped roof.
Half-hipped roof
A half-hipped roof.
Another way to merge roof styles is to use a gable roof for part of the height of a roof, and then switch to hipped for the remainder. This produces two variant roof types, the half-hipped roof and the Dutch gable or gablet roof, depending on which part uses which style.
For a half-hipped roof, you can 'switch style' at any point, producing a mostly gable roof with a very small hipped area, or mostly hipped. This half-hipped roof image shows 3 rows of gable roof and 2½ rows of hipped roof above it (including the layer of slabs at the roof peak).
Note how these buildings are significantly larger than the NPC village buildings, and yet if they were much smaller their variant roof styles would be difficult to recognise.
Dutch gable
A Dutch gable or 'gablet' roof.
The Dutch gable is a hipped roof with a (usually) small gable at the top. It's very common to put a small window in the gable part, but in this image we have used wooden planks for clarity.
Note that 'Dutch gable' is the common US term for this roof type, but this may sometimes cause confusion with the Flemish gable design described in the roof decorations tutorial.
Skillion roof
Skillion roof covering a porch.
A skillion roof is a roof surface which slopes in a single direction. It may continue the slope of an existing roof, or be separate. A skillion roof may sometimes be called a shed roof or lean-to. This image of a skillion roof shows a 1 in 1 pitch on the right hand side and a 2 in 1 pitch on the left hand side, allowing the roof to extend out over the porch without dropping to ground level.
Gambrel roof
A Gambrel roof. The dark wood shows the profile of a 45° roof for comparison.
A gambrel roof has two or three distinct roof pitches – steep lower down, and shallow or flat higher up. The result is that the usable volume under the roof is greatly increased. Some gambrel roofs may have one or more curved sections. If such a roof is partly curved and partly straight, it's usually the lower portions that are given curves first. These roofs would be hard to model well at normal Minecraft scales.
Gambrel roofs may also be known as kerb, curb or Dutch Colonial roofs.
Gull wing roof
A gull wing roof.
A gull wing or 'gullwing' roof has a shallow pitch lower down, and steep higher up. These roof designs often have extensive overhangs to help shade the building.
Mansard roof
A Mansard roof with three distinct roof pitches.
An alternative Mansard roof.
A Mansard roof is similar to a gambrel roof. It has two or possibly three distinct roof pitches – steep lower down, and shallow or flat higher up, but like a hipped roof it also has slopes in both the North-South and East-West directions. Some mansard roofs may use curved roof sections, more commonly on the lower portion. Hence the usable volume under the roof is greatly increased. Very large buildings may even have several storeys under a Mansard roof.
Some Mansard roofs may resemble bonnet roofs, having a lower part which is shallow, but which extends beyond the curtain walls. The key features of a Mansard roof are its squarish profile and its increased volume of roof space compared to a gable roof or other simpler design.
In Minecraft, buildings need to be quite large before Mansard roofs begin to look appropriate, especially as it's common to have an extended parapet around them. The building shown on the left is about 16×20 metres. With a parapet and just a 1m walkway all the way around, that would become 20×24m.
Bell-cast roof
A bell-cast roof.
Like a gambrel roof, a bell-cast roof has two distinct roof pitches, but it is shallow lower down, and steep higher up. It may also be referred to as a bonnet roof. Some bonnet roofs may be partly or fully curved, but this is hard to model at normal Minecraft scales.
Saw-tooth roof
A saw-tooth roof.
A saw-tooth roof has a series of ridges with dual pitches on either side. The steeper surfaces are glazed and face away from the equator to shield workers and machinery from direct sunlight. This type of roof is commonly used for deep plan buildings and factories. It may also be referred to as a northlight roof. Note that to be a 'proper' saw-tooth roof in Minecraft, the windows should all face North or all face South, and you should be consistent about which direction you choose.
Monitor roof
A monitor roof.
The same building, greatly changed in appearance by removing the overhanging eaves.
A monitor is a raised structure running along the ridge of a double-pitched roof, with its own roof running parallel to the main roof. The long sides of monitors often contain louvres or clerestory windows to help light or ventilate the building. This is a more common design for large buildings such as barns, warehouses and factories, and is not often used for domestic buildings. Note that the monitor does not necessarily have to run the entire length of the roof.
Helm roof
A helm roof.
A helm roof or Rhenish helm is a square roof with four gable ends. It is commonly used on towers. The building in this picture is 7×7 metres. To avoid gaps in the roof, slabs are usually needed under the main roof blocks. Here we use upper slabs made of quartz and lower slabs made of red brick. This design tends to work better with square towers of an odd width. Note also that the stair blocks should be placed to face in only two directions – North-South or East-West. Producing a good-looking helm roof with stair blocks facing in all four directions is very fiddly. For symmetry in both directions, it is usually simpler to just use ordinary blocks.
Butterfly roof
A 'butterfly' or 'London' roof.
A 'butterfly' or 'London' roof ('butterfly' appears to be the slightly more established term) is a V-shaped roof which was used in Georgian and early Victorian terraced houses. It is quite a common design in central London. Note that for a 'London roof', this roof shape placed at the back of the property. The central gutter tends to be prone to leaks. In this image the main roof has been made of red brick, and the borders with adjacent properties have been marked with dark wood.