To give you an idea of the results you can achieve with the Shape Generator Tool.
I copied one of your images onto the background in sh3d, estimated its size (width) at 35m (close???) drew some measurements onto it and used them to create the 3 shapes you can see in the image, 2 really, 1 is copied and mirrored.
The file can be downloaded from HERE, i hope it helps.
This method is not exactly a 1 click solution to creating a roof, but for a piece of software created about 14 years ago for positioning furniture in a room, it has in fact come a long way already.
