Prepare Roasted Lamb: Preheat oven to 325 degrees F. Rub leg of lamb all over with cut sides of garlic. In a small bowl, combine parsley, celery salt, pepper and paprika. Sprinkle parsley mixture evenly over lamb; rub in with your fingers. Place the lamb, fat side up, on a rack in a shallow roasting pan. Insert an oven-going meat thermometer in the center, making sure bulb does not touch bone. Roast, uncovered, for 1 1/4 hours.