@Emmanuel
Probably is not enough.

@Klaus60
1. You have to exercise before use a plugin, to understand how it work.
(any kind of plugin).

So,
2. For Roof generator:

1. open a new file sh3d
2. draw a room
3. select it
4. Go to Tools -> Generate roof...
5. work with roof
   [/list=a]Follow STRICTLY this steps and then we can continue to talk.
   Don't forgot: Roof generator work IF IS at least one room selected.
   
   I wish you success and don' be afraid to ask.
   Tomorrow you will the one who help me or others!