Unsupported eaves are generally recommended to reach no more than two feet (0.6 meters). However, that leaves a lot of unshaded and unprotected wall, especially for one-storey buildings. Dealing with sun in the tropics, one would be better off with 1.5 to 2 meters of overhang in an eave, for a 3 meter height roof.
This is easily done with brackets or corbells (a kind of bracket), which supports the overhang.
Corbells (and other kinds of brackets) can be made of a variety of materials, including cast stone, metal of various kinds. Corbells need to be at least 2/3rds of the supported eave in length, to properly cantilever. Example: 1 meter for a 1.5 meter eave.
Note: for exposed fasteners, need 3/12 slope.
Where will the water go
The biggest issue with a roof is where will the water go. Water needs to flow off of the roof, and any remaining moister needs to be able to dry out so that there will not be any rot. This seems obvious but when looking at how a roof (and connecting elements down to the ceiling) are constructed, it is not so simple.
Insulation of various kinds
Besides the roof and roof connecting material being engineered for water dispersal (and wind protection, and snow/hail in those specific climates), the insulating material is a key part of the system. Obviously having insulation become waterlogged can be quite hazardous so the first water dispersal properties must be done properly.
After that, there are various spraying, rollout, or manufactured panel insulation options. Natural wool is a great option, but of course it cannot get wet. It is important to consider the event of roof failure (that is, some parts of it come off of the roofing structure, such as in a hurricane or tornado, or simply a century storm). In the event of a roof failure there needs to be something that is waterproof that will remain. There are stick-on products that are popular in the US, especially dealing with regions such as Florida.
There seems to be two ways of dealing with insulation, which is having it built up as a part of the roof, or having it put in under the roof as a part of the ceiling in some way. It seems that in order to plan for roof failure, the insulation should be a part of the ceiling, and a sub-roof or stick-on environment be engineered beneath the roof.
It might be possible to deal with insulation in two parts. The first part -- the roof proper -- might a sort of metal sandwich roof (metal, insulation, metal -- though the lowest layer of metal could be a wire framework). The second part, the ceiling and insulated subroof itself covered with some kind of waterproofing. In between these two layers could be an air gap that could have airflow to increase insulating properties as well as keeping both components dry.