A roof is an architectural feature of a building.
In The Sims, a roof would automatically be generated when an area enclosed by walls was open at the top. Players could select a roof pitch and roof texture, which would be applied to all buildings on the lot. Beginning with The Sims 2, players had to add the roof themselves when building.
Several expansion packs allowed objects, such as weather vanes, to be placed on roofs.
In The Sims 2: Seasons, roofs are crucial to keep the elements out.