It is possible to CREATE 3D rooms in Revit based on 2D room geometry.
How? USE DYNAMO!
Its simply. Just add the nodes as shown in the image below.
Here is the best part……. the 3D Rooms are placed in the Room Category!!
Just Make sure you are using at least Dynamo Version .9x
Need to learn more? I will get into more depth about this and many other topics in my
“Practical Dynamo Class” at Autodesk University 2015 so make sure to attend.