Preheat roaster oven to 350 degrees. I always cook my turkey in a Nesco or similar type roaster oven as it keeps it juicy, doesn't heat up the kitchen, and leaves the regular oven free for baking other things. You can use the regular oven instead, just be sure to baste more frequently and tent the breast with aluminum foil during the final hour.
Boil the giblets in a small saucepan while the turkey is cooking and save the juice for the gravy later.
Rub turkey generously with olive oil and salt to taste. Sprinkle well with poultry seasoning and put plain sage inside the body cavity. I don't use a set amount, but I do coat it well with the seasonings. Place turkey on the rack place in the roaster. Bake for 3 1/2 hours, basting every 30 minutes after the first hour and a half. Remove from roaster and let rest for 15 minutes before carving.
If you wish to make gravy, pour the turkey drippings and giblet juices into a pan and mix in 2 tablespoons of plain flour. Mix flour in gradually to avoid lumps. Heat to boiling and cook for 5 minutes. If you need more gravy, add some canned chicken broth to stretch the drippings.