How long and at what temperature should I cook a beef roast in the oven? Roasting is a great cooking method for a large, tender cut of beef  such as a rib or sirloin roast.Sirloin-tip, rump, rolled-rump, eye-of-round or top-round roasts will also benefit from this cooking method if they are graded prime or choice.ooking at a constant oven temperature of 300°F (160°C), a 5- to 8-lb standing rib roast will take 17-19 minutes per pound for rare, 20-22 for medium rare, 23-25 minutes for medium, and 27-30 minutes for well done.