Preheat oven to 350 degrees F. Cook onions and celery in oil until tender, and them mix with other stuffing ingredients. Season roast. Place as much of stuffing into centre the roast as you can, allowing it rise almost as high as the points of the ribs. Place remaining stuffing into a lightly buttered casserole dish. Cover top of the roast with foil to protect tips of the bones from scorching. Roast 90 minutes, and then remove foil. At this point, put casserole of stuffing in the oven and roast the pork 30-45 minutes more, or until internal temperature of the meat has reached 165 degrees F. Let roast rest 10 minutes before slicing. Serve with apple sauce, or with gravy made from the juices in the pan.