Remove the roast from refrigerator 1 hour before cooking to reach room temperature. Trim all the fat off the meat. Using a sharp knife, pierce meat about 1/2-inch deep and insert slivers of garlic in each hole, pushing all the way in. Lightly spray the meat with olive oil and season generously with salt, pepper and rosemary. Place the thermometer all the way into the center of the meat.
Preheat oven to 350F. When the oven reaches 350F, place the roast in a roasting pan and put in the oven.
Roast until the thermometer reads 130° for rare, 140° for medium rare, 150° for medium, and 155-160° for well done. Remove the roast from the oven and let it rest 10-20 minutes before you cut it so that the juices distributed evenly. I personally remove my roast beef from the oven when it is 135° for medium rare. The temperature will rise an additional 5 degrees as it sits.