Dorin is the best one to answer questions about the roof generator.
He created a manual about dormers. You can find the urls in this post: https://sweethome3d.com/support/forum/v ... ,150#57575

There's nothing wrong with a roof in multiple parts. Sometimes it's easier to create it that way. You can always combine the parts and export/import them if you insist on a single objects for the roof.