Tips and Tricks: Start 1-4 days in Advance Read all the directions before you begin so you can plan ahead for the time required. When buying a roast, plan on about 1 pound of bone-in prime rib per person. You must have a roasting pan with a rack. You must have a thermometer, digital or traditional to read the internal temperature. Prime Rib has the optimal flavor at 130F. If you need a few slices of more well done meat simmer them in a pan of Au Jus until the desired doneness is reached.