Mat,

The short and more general answer is that they have taken an engineered framing system (roof trusses) and some amateur framers (because it is not the work of a "professional") have cobbed some conventional framing onto it. The whole system (trusses and the conventional framing being supported by it) needs to be engineered to do what they are asking it to do. There should be plans, permits, code inspections for this work on file ... if not, I'd recommend that a structural engineer evaluate the roof framing system and design repairs.

There's really not enough info in your post and photos to do a proper evaluation. From what I can see in the first two photos, one big thing jumped out at me. There does not seem to be anything tying the tails of the opposing conventional rafters together. That would make the ridge in the photos a structural ridge, and those support posts necessary to keep the roof from collapsing. As such, the posts should be turned 90 degrees and be full bearing on the ridge and truss as Jerry pointed out. An even bigger problem with those posts is that they are in poor locations -- you don't take a distributed load from the roof deck, turn it into a point load (via the posts) and then transfer that point load to the top chord of a truss without having appropriate web members of the truss directly under that point load to carry the load to an appropriate support below. I can only see one web in the photos -- it's near the front post -- and it is probably not adequate for the conditions, as created in the field, by the conventional framing that was added above it.

Brandon