Preheat oven to 450º. Wash the turkey inside and out with cool water and pat dry. Make sure to check the in the neck area for a bag containing the heart, liver and gizzard. Remove and save for gravy. Also remove the neck bone if in the cavity and save for the gravy. and Coarsely chop celery, onion, carrot, fresh parsley and loosely fill the cavity. Secure the wings. Salt and pepper outside and inside of the turkey. Lightly coat the roasting rack with cooking spray. Place turkey breast side up in roasting pan. Brush turkey with melted butter or vegetable oil. Place the pan in the oven on lowest rack and then reduce temperature to 325. Allow 15 to 20 min per pound for birds 7 to 15 pounds. Loosely cover breast with lightweight foil when about 2/3's done. Turkey is done when meat thermometer is 170º in thick part of breast. Cover turkey with foil and let turkey stand for 15 min prior to carving.
For gravy, if the turkey came with the neck bone, gizzard, and heart, then rinse and place in medium pot. Add 3 to 4 Cups water and add 1/4 C chopped onion and 1/4 Cup chopped celery. Let simmer for 1 hour. Then strain the broth and set aside till turkey is baked. Once the turkey is removed from the roasting pan pour strained drippings from roasting pan into 4 - cup measuring cup. Add enough broth from the neck and gizzard to drippings to make a full 4 cups. Cook and stir until gravy comes to boil. Thicken with flour and cold broth. Season salt & pepper.
If use roaster: remove insert from pan and preheat roaster to its highest setting.
Prep turkey by rinsing and patting dry. Place bird in insert pan on top of the wire rack. Make sure handles are up.
Rub the entire bird with olive oil so it will brown. Put the vegetables in the turkey and salt and pepper. Some use poultry seasoning on the turkey.
Put the insert pan with the bird into the roaster oven and cover. Do not add water.
Roast at highest setting for 30 min so the bird will seat and brown the skin. After 30 min turn the roaster down to 325 degrees. Do not lift the lid. Figure your cooking time.
8 to 11 lbs 2 3/4 hours, 12 to 14 lbs 3 hrs, 14 to 18lbs 3 3/4 hrs.
Check temp when about 3/4 done. Want 180 degrees in thigh or 165 degrees in breast.
Once done, remove turkey from roaster and cover in foil and let rest 20 min.