The first is the 3d preview in the select rooms and the second is the roof in select roofs.
Hi @cherry, welcome to the forum.
Hmm. The fact that the 3D model walls comes with an arc shows that the roof is there. It might be a visualization issue. For a roof like this, the better workflow is to quickly simplify the roof in Rhino and import it back to the Model Editor. If you can share the PoMF with me, I can have a closer look.