I exported the model from Rhino 8 with interior lighting, then in UE5 architecture, the roof is invisible when viewed from outside. However, when placing the camera inside the building, the roof is showing up correctly.
Open the roof material and check the Double Sided checkbox.
Basically the material is one sided, so you only see it from on or the other. In Rhino you can make a backface view so you can see which normal direction your surfaces are facing.