Roofs are both confusing and annoying, one of the worst parts about building, if you ask me. Just a question, is the room underneath it complete? That can sometimes mess up roofs. My suggestion is to just mess around with it, see what happens, something should click into place ... eventually.
Dunno if this helps, not much of a builder, I hate building but I know how frustrating it can be (Building is probably what I rage quit over the most, lol) so I thought i'd stick my ten cents in, in the hope it helps somewhat. XD