I made a little egg and now I'm cuddling like a hen.
@Mike53 Thanks for inspiration!
@Emmanuel & @youseeus Thanks for moral support!
I wasted a month struggling with some angles but finally I made something.
The most important thing is that I found a direction:
- stright-skeleton
- 2D polynons
- 3D polygons from 2D polygons
- 3D object
Another thing was to cut back on claims. I preferred it to be something (imperfect) than nothing.
That's what I've done so far:

I start with failures:
The thin red lines are unclosed polygons and thick red lines with arrow are wrong polygons.
The blue polygons are good 2D faces

Few acceptable


Finaly the Roof Generator plugin beta
After installation select a room and Tools -> Generate..Bla..Bla...