Preheat oven to 225℉.
Bring tri-tip roast to room temperature.
Place olive oil and garlic in a small saucepan. Bring to a simmer on low/medium heat and cook until garlic turns soft and golden. Remove from heat, drain oil (reserve oil for future uses) and add kosher salt. Mash garlic into a paste.
In a mixing bowl combine spices for dry rub. Rub mix all over tri-tip then spread garlic paste all over tri-tip.
Place tri-tip on a wire rack ontop of a sheet pan. Roast in oven for 1½ hours, or until internal temperature of roast reaches 120℉. Let the roast rest for 5 minutes.
In a preheated castiron skillet melt ghee on high heat. Once ghee begins to smoke sear tri-tip on all sides for 30 seconds per side.
Remove from heatr and let rest 5 minutes before slicing thinly against the grain. Leftovers make a great sandwich or salad!