While I initially thought there was a way to do this, I have recently come to the conclusion that this isn't possible. And some of the scale differences between roof styles are ludicrous.
I was trying to build a colonial style plantation house, with octagonal "towers" on the front corners. The domed roofs didn't look right on the towers (you can't control the pitch of those), but the octagonal roof looked nice. I wanted to use that gable roof (the one with the wall on the long side, I don't remember the name just now). But with the width of the house, the main roof would be 3 1/2 stories high unless I wanted a virtually flat roof on the towers.