A prime rib should cook for about 15 minutes per pound if cooked at 325 degrees Fahrenheit. If it is cooked at 450 degrees to start, it takes about 13 minutes per pound.
A prime rib is a very tender cut of meat if cooked correctly. Sear the meat by turning the oven to a high temperature for 30 minutes. Afterwards, cut the temperature down and allow the meat to cook for 13 to 15 minutes per pound. The meat should reach an internal heat of 140 degrees for a medium-rare roast. Once the meat is done, let it rest for 15 minutes.