Generously rub salt and pepper over entire roast, lightly coating the ends.
3 ribs or under: Roast at 325 degrees for 18 minutes per pound, or until internal temperature on meat thermometer reads 115-120 degrees for rare, and 130 degrees for medium rare.
Over 3 ribs: Roast at 275 degrees. Check with meat thermometer after 1 1/2 hours. Internal temperature should be 115-120 degrees for rare, and 130-140 degrees for medium.