Preheat oven to 325 degrees F. Trim fat from roast. For rub, in a small bowl combine mustard, garlic, rosemary, salt, and pepper. Sprinkle rub evenly over all sides of the roast; rub in with your fingers. Insert an oven-going meat thermometer near the center of the roast. Place roast on a rack in a shallow roasting pan.
Roast for 1-1/4 to 1-1/2 hours or until thermometer registers 150 degrees F. Cover roast with foil and let stand for 15 minutes . The temperature of the meat after standing should be 160 degrees F. Makes 6 servings.