Normally, here is how I roast a turkey, and while this looks long and complicated, it's not. It's easy breezy. I've done this for at least eight Thanksgivings in a row, plus Christmases, and I can honestly tell you that the hardest part is figuring out then the sucker's done.
Roast Turkey and Giblet GravyWash the turkey with plain water (if it was frozen, give it at least a week to thaw -- that means it should be in your fridge today). Pat dry with paper towels.
Remove the parts bag from inside the cavity. Reserve for later.
Place him on a rack in a large roasting pan. Stuff his clean cavity with a large quartered onion, several 3-inch long pieces of celery and a half dozen peeled garlic cloves**. If his legs are not tied together, tie them with some cooking twine. You could get fancy and really truss him up, but I find tying his legs together is fine. If you want to eat your wings, truss him up (otherwise the wings get too done. No one eats ours, so I don't care).
Rub his skin (breast and legs) with softened butter (about 6 tablespoons for a 15 lb. turkey). Sprinkle generously with salt and pepper.
Pour 1 to 2 cups vegetable broth in the bottom of the roaster. Roast at 400 degrees F. for 45 minutes. Turn oven down to 325 degrees F. and roast until done (here's a good timetable), basting every 30 minutes to one hour with the broth in the stovetop cooking liquid (I'll get to that in a minute). If the turkey starts to brown on the outer edges, tent a piece of foil over the top.
I have never been able to cook a turkey in the amount of time recommended. It always takes longer. Maybe because I baste every 30 minutes. If you baste, you need to allow more time (because the oven temp drops each time you open the door). I usually allow at least an hour longer than recommended.
For the stovetop cooking liquid (ultimately for gravy), take the extra parts (including the neck) and put them in a pan of water (about 5 or 6 cups). Salt and pepper and bring to a boil; cover and simmer on low while the turkey cooks, adding more water or chicken, turkey or vegetable broth as needed. Use this liquid to baste the turkey.
Now, my mom always makes the Thanksgiving gravy (even though I can make a perfectly good gravy). And, the recipe for gravy really depends on how much broth you have at the end. But, I'll give you a rough recipe -- to be adjusted for your own broth.
Strain stovetop cooking liquid, reserving the "parts." After you remove the turkey from the roaster, strain the liquid from the bottom into the stovetop cooking liquid, removing the greasy liquid on top. Heat to a simmer. Dissolve several tablespoons (this depends on how much liquid you have from your turkey -- start with 3 or 4 tablespoons) flour into about 1 c. cold water -- stir until smooth. Stir flour mixture into hot cooking liquid and stir with a whisk. Bring to a simmer and if gravy is not thick enough, repeat with more flour and cold water, a little at a time, until desired thickness is achieved. Be sure to bring it to a boil each time you add flour water, as thickening will not occur until gravy boils. Taste and season with salt and pepper and onion powder if needed. The key to no lumps is adding cold liquid to hot liquid -- never the same temp.
If you want giblet gravy -- cut the cooked parts up into tiny (I mean tiny) pieces, including the neck meat, and add it to the finished gravy. If this grosses you out, no giblets.
**I do not stuff the turkey. I would never be able to eat it if I did, because I would never be confident that it was completely cooked. Since I can barely get the turkey cooked completely, imagine if it were stuffed. I know some people cook their turkey all day just to get the stuffing done, but that seems as though it would result in dry turkey. I'd rather just cook the stuffing in a casserole.