Remove thawed turkey from the packaging. Remove the neck and giblets (check both body and neck cavities) and save for later or toss.
Pat the turkey with paper towels to completely dry the inside and outside.
Preheat your oven to 350°F (or whatever the instructions on the roasting bag says).
Soften butter and mix in salt, pepper, garlic, sage, rosemary, and thyme.
Using your hands, loosen the skin over the breast. Spread as much of the herb butter mixture between the breast and the skin. Spread any remaining butter on the outside of the skin.
Season the cavity with salt, pepper, sage, rosemary, and thyme.
Stuff the cavity with apples, onions, and celery.
Insert the meat thermometer into the thickest part of the breast and place in the roasting bag. Put in the roasting pan.
Roast until the thermometer reaches 165°F. (It usually takes about 15 minutes per pound.)
Remove from the oven and cut the bag away from the turkey. Let stand for 45 minutes. (Trust us on this one, you don't want to cut it too soon and lose all the juices!)