In a small bowl, combine the tomato sauce, chili paste, oil, spices and garlic.
Trim the fat from the roast. Place the meat in a shallow dish; sprinkle with salt and pepper. Spread the spice paste over both sides of the meat. Cover and marinate in the refrigerator for 2 to 6 hours.
GRILL:
Preheat a gas grill to 350℉. You'll be using direct and indirect grilling for this recipe, so just turn the burners on half the grill.
Place the seasoned tri tip roast directly on the grill grates over indirect heat. Close the lid and grill for 30 to 40 minutes, flipping every 6 to 7 minutes. When the roast reaches an internal temperature of 120℉, move it over to direct heat and grill for 2 to 3 minutes per side or until the internal temperature reaches your desired doneness. Pull the tri tip from the grill when it reaches a final temperature of the following: 125℉ for rare, 135℉ for medium rare, 145℉ for medium, 155℉ for medium well, 160℉ for well done
Remove the tri tip from the grill. Rest the meat for 10 minutes then slice against the grain and serve.