Wow! Do you know if the house originally had the vaulted ceiling? It almost sounds like it might have originally had trusses and that these were hacked up to create a tall ceiling. First, there is no excuse for having roof rafters this small. If it was originally framed this way then it was not built to code. If it was later altered, then whoever did in violated the law. The original builder might be past the amount of time where you can sue him, but if it was altered relatively recently then you might be able to recover damages for repairs.
This is what is happening: Your house is falling down. If you want to build a cathedral ceiling (a building with no collar ties, or ceiling joists) then you have to put a large, structural beam at the roof ridge to "hang" the roof rafters on. In a house with no ridge beam for support, the roof presses down and forces out the walls. The ridge cannot sag like this unless your exterior walls are falling out. You need to beef up your rafters by sistering more substantial framing onto them because they are much undersized. You also need to stop your walls from falling over. You need to take many "come alongs" that stretch from ext. wall top plate to top plate and slowly crank the walls back in. You then need to do one or more of the following: put in collar ties or collar beams to hold the walls in; put a ridge beam to hold up the roof, or get all new trusses or a whole new roof framing; get a couple sticks of dynamite.
This is very very bad and very very shoddy building. If you can find who did this, you should be entitled to sue them for the cost of repairs. I am not sue happy, it is just that this house is either going to fall in or cost you many tens of thousands of dollars to fix.