While waiting for my code to compile at work, I broke out a couple pages from last year's daily cat calendar and mocked up a system for making some roof pieces that could fold flat, but easily form some more interesting roof lines.
I rough-cut four triangles and taped them together. In reality, I assume I'll be able to either cut this all out of a single sheet of cardstock, or if I can get get a two-ply piece off of one sheet, I'll design it so it's half on one page, half on another and have a tab to glue them into one piece.
I added a couple pieces that look a lot like the tabs that are on the sides of the Terrainlinx walls.The idea is that these would fold inward, and I'd slide a cardstock piece over them to lock them together. Here it is assembled:
Nothing radical, but it does make me believe I should be able to make more roof pieces that fold flat, but let me cap off different types of tiles.
I will make a full scale 3" tile-based roof out of cardstock to night to see how it would really fit.