A good rule of thumb for purchasing bone-in prime rib is to buy one pound per person. A bone-in standing rib roast will feed about two people per bone. But if the roast is part of a bigger spread ...

you cook a prime rib roast at 500 degrees for 5-6 minutes per pound, then turn the oven off and leave the door closed for two hours. At that point, the temperature of the prime rib will be perfect ...