@dorin, thank you very much for yours Effort.
I selected the walls and not the rooms !!
Now the roof generator works !!
So now I have my next problem - the shape of the roof.
I took some pictures and uploaded.

https://www.mediafire.com/view/jlwwblln ... 2.JPG/file
https://www.mediafire.com/view/pj2kh96c ... 3.JPG/file
https://www.mediafire.com/view/thnye8ke ... 8.jpg/file

Maybe you also have an idea?

Regards Klaus