So, I've been so consumed with modifying the roof and truss pieces that I'm not sure I've thought through the fact that maybe the roof pieces don't need to change at all, and the trusses can remain the same way they are. Instead, what if I created some simple pieces that slip around the truss, covering the texture with the texture from another roof?
I don't know if they'll be too annoying, but this is what I'm thinking. Make something that slips up through the bottom hole of the truss. It would extend all the way to the top of the truss on the inside, and on the outside (where it's textured) it would extend maybe ¼" past the top of the truss. You'd fold that ¼" into the truss, then slide the roof in place. That would hold the covering in place.
I am guessing the whole idea will be too flimsy to hold up, but I figured I'd note it in case everything else fails and I need something to come back to. :)
-OR- why not just make a piece that attaches to the roof, but covers the truss area? I'm thinking that a piece about 1 ½" long, with a ¼" flap that folds under so that the whole thing is raised a little. I don't know if it will look Frankenstein-ish or not, but this seems like the most trivial adaptation to make roof pieces work better with TLX trusses. I am not sure if the flap that raises the texture up over the truss would have to be 2x thick or if just 1x thick would do. It might get lifted up a lot and look ugly if it's not right, but it might look ugly anyway if it's really noticeable. Doing it this way would mean not remaking ANY pieces, though. It would just mean adding a simple piece on top of the simple roof pieces. It might also mean it would hide some of the ugliness of TLX roof/truss joints, where they don't QUITE line up right.