Hi Jerseydude, Fishing the Snake River I know all too well the difficulty of fishing on a rocky bottom. I would suggest scouting spots on the river and look for eddys and current changes. Also look for sandy or muddy bottom areas that are a main highway these fish use to move up and down the river. Usually located at the dropoff between shallow water and main channel.
Dragging a 1oz sinker across the bottom of river will quickly tell ya what kind of bottom there is. This well allow you to eliminate the more snaggy areas.
There are rigs best utilized for these rocky,snaggy areas,but I would suggest using a bolt rig or sliding sinker setup, if you can find a more friendly fishin' hole.
If not a 3 way swivel with the sinker tied to the bottom most eyelet,using a light test mono,will work good. When the rig becomes hung up, the sinker is usually to blame. Which is why the light mono, the sinker will easily break free and allow the rest of your rig to be retrieved.
As far as hook size, I like to use size 2 for BFC's For smaller fish,size 6-8 should be good. Just use the best quality you can. A monster carp will find the weak _link_ in your rig very fast! I like Gamakatsu or Daiichi.
Perhaps NJCarpFisherman could shed some light on this?