Sprinkle roast on all sides with garlic salt, seasoning salt, black and white pepper; knead into meat (do not punch holes in the roast.) Place roast, fat side up, on rack in roasting pan. Insert meat thermometer, making sure the bulb does not touch fat or bone. Bake uncovered, at 325 degrees, for approximately 3 to 4 hours. Roast to internal temperature of 150 degrees for medium rate and to 160 degrees for medium doneness. Remove from oven. Trim fat from roast. If desired; bake at 400 degrees for 10 minutes or until browned. Slice roast and place slices on hot serving platter. Garnish with spiced apple rings and parsley.