Rather than make NEW trusses and NEW roof pieces, I opted to simply cover existing roof pieces and trusses. Here's a picture of a thatched roof in a Thoumont's truss:
1) If you've made any trusses already, you won't have to redo them.
2) If you've never made them before, you can follow the TLX instructions.
3) They're fully textured inside and out, and are really sturdy.
I also didn't modify the roof at all. Well, sort of. What I've done is created a rectangular piece that covers the existing roof as well as the truss. Here's a picture of the roof, upside-down:
1) You can continue to use your roofs as-is!
2) You can upgrade your existing roofs very easily, and start using them on other trusses!
3) The modification is very simple to perform - no complicated cuts or fiddly assembly!
Here's one more shot from the front, showing that the roof piece completely covers the tops of the two trusses it is slotted into:
So, I'm moving ahead this this design this week.
Quick update to show what this would look like with a 2-way truss supporting two roof pieces.