I know you can use various addins (like Case Extrude Rooms to 3D Mass) to make a form out of a Room element in Revit. However, there is a vanilla Autodesk way you could go about this:
Export a Revit view to Navisworks with all of the Room-related export boxes ticked in the Navisworks Exporter addin
Open / append the NWC in Navisworks
Turn off everything except the Room objects that the Navisworks Exporter created
Export the scene to FBX, convert to DWG, import it to a family, place that family back in the project (using parts of this workflow). Use origin-to-origin linking to get things right.
You could then use the Room 3D element “family” in an Interference Check, to determine what elements exist in Rooms (this would only work for Categories that support Interference Check in Revit).
