For a 3-4 pound sirloin roast, bake it for 2 to 2 1/2 hours for medium well. A 6-8 pound roast should bake for 3-3 1/2 hours for medium well.
The main way to cook a sirloin roast is by baking it the oven. Put it in the oven at 325 degrees Fahrenheit.
Sirloin roast can also be cut into a steak for other cooking options, such as pan cooking. If the roast is an inch thick, cook it for 30 minutes if you want it medium well. A sirloin steak that is 1 1/2 inches should cook for 25 minutes.
If you decide to grill it, do so on medium-high heat. It should be cooked for 7-9 minutes for a 1-inch steak, 12-15 minutes for a 1 1/2 inch steak or 17-19 minutes for a 2-inch steak. These cooking times are average time to cook the steak to medium.