Brush the oil over the surface of meat. Generously sprinkle the seasoning over the meat and rub it in.
Cook the roast over a hot grill until the meat reaches your desired doneness. 145 degrees is considered a safe internal temperature.
Meanwhile, cook the garlic bread on the grill, wrapped in foil, for about 15 minutes. Open the foil and crisp the cut sides by turning them upside down on the grill for a few minutes, watching for flare ups.
When the tri-tip is done, remove the roast from the heat and allow it to rest for 10 minutes before slicing. Slice it thinly.
Layer thin slices of meat onto one side of the grilled bread. Place the top and cut the loaf into four sections.
Serve the sandwiches with the salsa.
Promptly store leftovers in an airtight container in the refrigerator, for up to 4 days.
Nutritional values are approximate and based on 1/4 the loaf.