Sauté sausage in heavy large skillet over medium-high heat until cooked through, crumbling sausage with back of spoon, about 10 minutes. Using slotted spoon, transfer sausage to large bowl. Add butter, onions and celery to skillet; sauté until onions are tender, about 15 minutes. Add apples; sauté until apples are tender but still hold shape, about 10 minutes. Add sage, thyme and allspice; sauté 1 minute. Add to sausage. Stir in stuffing mix. Season with salt and pepper. (Can be made 1 day ahead. Cover; chill.)
Preheat oven to 325°F. Generously butter 5x10-inch glass baking dish. Fill center of crown roast of pork with stuffing. Transfer remaining stuffing to prepared dish. Cover with foil and bake until heated through, about 40 minutes.
