It's perhaps worth saying too that rooftops are rooftops, and haven't changed a tremendous amount over time, within a fairly limited range of forms (flat, sloping, domes/spires). In the basic City Designer 3 package you already have the option to draw your own rooftop (= house) shapes, using a variety of textures, so you can add exotic shaped pieces/materials to any ordinary roof to make them look weirder. If you'd prefer ready-made domes in a variety of colours and textures, try the bonus issue of the 2018 Cartographer's Annual, City Domes.

Don't forget too to explore the house symbols style options in CD3 anyway - Classic (loosely ancient Greek-Roman), Mideast, Thatch in the Bitmap A collection; Classic, Fantasy, Hovel and Thatch in the Bitmap B set; some of the Gothic items in both could provide some especially weird structures as well; many of the Vector symbols could be used in this regard too.