Lots of different ways, but here's a way that keeps it simple and works every time for me with great results:
1) Season your roast (I like to rub with a little brown mustard, season it with either Little Louie's or salt, pepper, garlic & rosemary). DON'T worry about letting it come to room temp; it's NOT necessary.
2) Insert a temp probe into the middle, put it in the smoker at 275° and let it go until it reaches about 8° - 10° below your final desired internal temp. This will take somewhere around 3.5 - 4 hours depending on how big the roast is and at what temp you pull it off.
The temperature will continue to rise from the carry-over heat, so as a guideline, for:
Rare pull it off around 120°
Med-rare: 127° - 130°
Medium: around 137° - 140°
Anything more than that and it will start to toughen up.
3) This is the MOST crucial step: LET IT REST for a MINIMUM 30 - 45 minutes. I like to use scooter's trick: I leave the temperature probe in it until the temp levels out and starts to drop. Then I know for sure the muscle fibers have relaxed and it'll be nice and tender when I slice it.
This works for more than just Rib Roasts too. I just did a Strip loin the same way:
Thanks,TentHunter, I just put it on. I am going to put it on smoke (Traeger Texas) for two hours, then raise to 275 until probe says 135 then let it set. I do a lot of briskets, but never have done a prime rib. Got my fingers crossed.S
I do the same except at 225 to 250 on my Traeger. Then while resting I crank up the oven to high. When the roast starts to cool I throw it into the oven for about 20 minutes to get a nice crust on the outside.