Position a rack in the lowest part of the oven; remove the other racks and preheat to 350˚. Put the turkey neck, celery, carrots, 6 wedges each onion and apple, half of the sage and half of the parsley in the center of a large roasting pan, creating a mound for the turkey to sit on. Stuff 2 tablespoons butter, the remaining 2 wedges each onion and apple and the remaining sage and parsley inside the cavity of the turkey. Place the turkey breast-side up on top of the vegetables.
Combine 1 tablespoon each salt and pepper in a small bowl. Pat the turkey dry and season all over with half of the salt and pepper mixture. Spread the remaining 6 tablespoons butter all over the turkey, then sprinkle with the remaining salt and pepper mixture. Tie the legs together with kitchen twine and tuck the wings under the body. Pour 1 cup water into the roasting pan around the vegetables.
Roast the turkey 1 1/2 hours, then baste with the pan drippings. Continue to roast, basting every 30 minutes, until the skin is crisp and golden and a thermometer inserted into the thigh registers 160˚ to 165˚, 45 minutes to 1 1/2 hours more. (Tent with foil if the skin is browning too quickly.) Let rest 15 minutes in the pan.
Carefully tip the turkey so any juices pour into the roasting pan. Transfer the turkey to a cutting board and let rest at least 30 minutes before carving. Remove the vegetables and herbs from the roasting pan and use the drippings for gravy.