Don't expect too much!
As I promise I've try another approach: planes intersections.
There is advantages and disadvantages.
Anyway few words and pictures for this version:
It work for few simple roofs: rectangle and shape L, T, S, F(as described here).
Don't work as expected on complex shapes like E or round.
The angle could be adjusted before add roof to home plane.
The blue edges could be made invisible when You set texture.
BUGS:
-Sometimes make SH3D unresponsive;
-Texture coordinate are wrong on north faces;
-The interior face of roof are transparent.
Also on SurceForge .