Sprinkle rub on all sides of the tri-tip roast. Coat generously and massage the rub into the beef.
Wrap the seasoned tri-tip in plastic wrap (or cover with foil) and let it rest at room temperature for at least 1-2 hours.
Preheat grill to 450°F.
Sear seasoned tri-tip on all sides, typically rotating after about 3-4 minutes per side. Pay attention to which side of the roast is fattiest - this side will tend to drip into your flame more and might cause flare ups.
Remove roast from your grill and place on a plate. Change temperature of grill to 250°F. (You can substitute an oven at 250ºF for this part if you prefer to not use the grill)
Once the grill is steady at 250°F, place roast back onto grill. Cook until roast reaches your desired doneness. Typically Santa Maria Tri-Tip is served medium rare (take off grill after 130°F internal temperature is reached) or medium (after 140°F is reached). This phase can take about 30-50 minutes depending on how large your tri-tip is.
Remove from grill and allow to rest at room temperature for about 10 minutes before slicing. Slice, serve, and enjoy.