To roast a trip-tip, begin by preheating the oven to 425 F. While the oven is heating, heat a large pan on the stove over high heat. Place the tri-tip with the fat side down on the pan, and lower the heat to medium-high.
Sear the tri-tip for about four minutes. Turn it over, and place it in a baking dish with the seared side facing up. Cook for 30 minutes for rare or medium rare meat or 45 minutes for well-done. Use a meat thermometer to check that the internal temperature is between 135 and 150 degrees, then emove the meat from the oven and place it on a cutting board. Cover the meat with a piece of aluminum foil, and let it sit for 15 minutes to allow the juices to settle before carving it.
To give tri-tip extra flavor, marinate it before roasting. Mix together 2/3 cup of vegetable oil, 2/3 cup of honey, 1/4 cup of Worcestershire sauce, 1/3 cup of red wine vinegar and one package of tenderizing marinade. Add 1/4 teaspoon of salt and 1 teaspoon of ground pepper, and pour the mixture over the meat. Marinate for six to 24 hours. Rub the meat with 1 teaspoon of garlic powder and 1 teaspoon of crushed rosemary, and then roast as usual.