Remove roast from fridge, pat dry with paper towels, and let it rest at room temperature for 1-2 hours.
Preheat oven to 450°F.
In a small bowl, mix rosemary, salt, pepper, onion powder, and garlic powder together. Add butter and mix thoroughly.
With a spatula, spread the butter mixture over the entire roast. Insert digital thermometer. into the center of roast, away from the bone.
Place the roast in a roasting pan (or large skillet) on a rack and cook for 15 min at 450°F. Reduce heat to 300°F and continue cooking until the internal temperature is 120°F, approximately 30-45 minutes. Note: check the internal temperature after 25 minutes if your thermometer is not in the roast during baking.
Remove from the oven and cover with aluminum foil and let it rest for 15-20 min and the internal temp rises to 130°F. Slice and serve!
Leftovers can be stored in an airtight container in the fridge for up to 5 days.