The best way to cook prime rib is to roast it in the oven. This beautiful, classic, dish should first be placed on a heavy roasting pan and then place it in a 450 degree oven, searing all sides. Then lower the heat to 325 degrees and continue to cook for 13 to 15 minutes per pound. The internal temperature of this boneless cut should reach 140 degrees, or rare. Let stand for 15 to 20 minutes before cutting.