Caren,
The tool most capable of controlled plastic forms in Archicad
is the mesh tool. It can do twisted roofs quite well with the
help of SEO. More problematic are twisted walls which imply
wall openings. The mesh tool cannot make holes through
the sides of a mesh. The Maxonform add-on can make
twisted forms. I have not tried it so I do not know
it's capabilities and limitations.
You might try a search using the key words "mesh and roof".
Peter Devlin