The two major categories of roof are flat and pitched and one of the main things that will determine the actual style of roof you need is the shape of the building.
How to build a small round roof.
The half round tower opens into the first and second floors on the inside but it becomes full round construction where it penetrates the roof.
Learn how to build with a variety of natural building techniques.
The turret projects from the front elevation and encloses a stairwell with semicircular mid level landings between floors.
It will be much more difficult to build a round roof onto a square building for instance so allow the shape of the structure to guide you.
Light earth strawbale cobb roundwood timbers reciprocal roofs lime and mud renders and more.