Lay tri tip roast on a large baking sheet. Whisk together remaining ingredients into a dry rub. Rub all over roast and refrigerate 3-4 hours or overnight. Remove from fridge and bring to room temperature before grilling.
Prepare grill or Big Green Egg to 250 degrees. Place tri tip on grill, with a digital meat thermometer inserted into the larger end of the roast (I used the MEATER+, which is a fantastic device), close the lid and let cook 20-25 minutes until internal temperature reaches 115-117 degrees, preferably on indirect heat. Remove from heat and place on baking sheet.
Turn grill or Big Green Egg up to 500 degrees, and sear roast on direct heat, 2-3 minutes per side, until internal temp is 145 degrees (medium) or 150 (medium well). Remove from heat and let stand 5-10 minutes. Slice, then serve, reserving excess juices for pouring over meat.
Notes
The Tri Tip cut of sirloin roast is also called a Triangle cut. If you are unable to find this cut of roast (I'm talking to you, East Coasters), then you can make this recipe with a Chuck Roast, a Rump Roast, or a Sirloin Roast.