Jerry,

After I wrote my question, I did find some other sources that refer to a couple of method of attaching the rafters to the sidewalls that counteract the stress that would push apart the side walls.

However, I'm still confused about what handles the roof load. If I get it right, in a traditional gable style house with a flat ceiling, the roof load is carried down the rafters to the side walls.

So are you saying that in a gable style house with a cathedral ceiling and a structual ridge beam, that roof load is now carried by whatever supports that ridge beam (the gable wall)? Or does the majority of the roof load still travel down the rafters to the side walls? I guess my question is, do the gable walls in a house with a cathedral ceiling and structural ridge beam(s) now become the main support walls?