Tri-tips weigh approximately 2-3 pounds, depending on size and how much fat is on it. When I am roasting a tri-tip in the oven, I trim most of the fat off the roast. I like to cook this bad boy at a high temperature, 450ºF. This creates a nice crust around the roast. The roast is done after approximately 45-minutes, or until it reaches an internal temperature of 135º-140ºF for medium-rare  and 140º-145º F for medium.