I agree with those who say don't go straight from the fridge to the smoker. Reason being, you put a cold roast in the smoker (especially prime rib where you want that constant pink med-rare throughout the whole roast) the outside will be overdone by the time the center of the roast hits med-rare because the middle of the roast will take considerably longer to reach 120 degrees than the outside of the roast if it is put on cold. Conversely, the outside of the roast will continue to cook and over cook while the middle is getting to medium rare.
Result, you have a small medium rare center surrounded by well-done exterior. You want the whole roast to cook to medium rare at almost the same time so you have lovely pink all-the-way-through slices that everyone associates with prime rib. So bring up to room temp before you throw them rib roasts on.
LG BGE-Brinkman Cimmaron-Custom Pull-behind (old grade school boiler)-Weber Kettle-DCS 30"