In a preheated 375 degree oven roast prime rib for one hour, uncovered,then TURN OFF OVEN, LEAVING ROAST INSIDE BUT DO NOT OPEN THAT OVEN DOOR !!!!! Let roast sit in oven for 3 hours, but remember, DO NOT OPEN THAT OVEN DOOR !!! Youll need to set your timer for 3 hours EXACTLY......!!!!!