how long does it take to cook a prime rib roast in the oven
Roast in oven until thermometer registers 115Â°-120Â°F for rare or 125Â°-130Â°F for medium. (The internal temperature of the roast will continue to rise after you take the roast out of the oven.). Check the temperature of the roast using a meat thermometer 30 to 45 minutes before you expect the roast to be done.For example, with a 10 pound roast, you would expect 2 1/2 hours of total cooking time (15 minutes at 500Â° and 2 1/4 hours at 325Â°).oast in oven until thermometer registers 115Â°-120Â°F for rare or 125Â°-130Â°F for medium. (The internal temperature of the roast will continue to rise after you take the roast out of the oven.). Check the temperature of the roast using a meat thermometer 30 to 45 minutes before you expect the roast to be done.