Trim the large chunks of fat (or have your butcher do this) from the tri-tip, and cut the thin silvery skin off if you can. Rub the salt all over the tri-tip.
Combine the remaining seasonings (except the olive oil) in a small bowl and rub into the tri-tip. (*It will seem like a lot, but that's a good thing!).
Pour 1/4 cup of olive oil in a large resealable plastic bag. Place the spice rubbed tri-tip in the bag with the olive oil and rub it in to coat completely. Squeeze out as much air as possible and seal. Place in the refrigerator for 5-6 hours, or up to 24 hours.
When ready to grill, preheat an outdoor gas grill to 350-400 degrees F. Remove the tri tip from the refrigerator and let it come to room temperature while the grill is heating. Wipw off any excess marinade with paper towels.
Place the tri-tip directly over the flames on the hot grill. Close the lid and watch for flare-ups.
Cook approximately 8-10 minutes per side for medium rare. It can take up to 20-25 minutes to cook a 2 pound tri-tip, so check the internal temperature (120 degrees for rare, 130 for medium rare and 140 for medium), or in a pinch use the flesh test (see post).
Place the cooked roast on a cutting board to rest, covered loosely with foil, for about 10 minutes.
Uncover and cut in half, where the grain changes direction, then cut each piece against the grain into 1/2 inch slices.
Check for doneness using a digital meat thermometer.
120℉ for rare
130℉ for medium rare
140℉ for medium
150℉ for medium well
160℉ for well done
Very important to let the tri tip rest before slicing and make sure to slice against the grain. This means you need to change direction around the middle of the roast.