Rotate stand-alone wall and roof

It would be nice if we could have stand-alone wall and roof segments that we could then slope and whatever angle we needed. Right now I am trying to build a tower that gradually narrows as it goes up and I am having trouble getting the walls of the tower right.
The roofs don't slope up from the lower floor toward the upper floor properly. The roofs look like they would just collect water up against the tower wall.