Evenly rub turkey parts with oil. Sprinkle with salt and pepper. In a large roasting pan, place turkey, skin side down, in oven and roast for 45 minutes.
Prepare and combine vegetables. Reduce heat to 350 degrees F, briefly remove turkey, add in vegetables, turning to coat in bottom of pan juices. Place turkey, skin side up on top of vegetables and continue to roast for another 35 minutes.
Remove pan from oven, place over burners and add in 4 quarts of water. Scrape bottom of pan to remove stuck bits, repositioning turkey and vegetables as needed. Keep at a medium to low simmer for 2 hours, uncovered until deep in color and flavor. Strain turkey and vegetables from stock, pushing any vegetable matter through strainer. Let sit, and skim fat from top.
In a large saute pan, melt butter, stir in flour, and cook for 1 minute. Slowly add in warm turkey stock 1/2 cup at a time until gravy is desired consistency. Add in spices and adjust seasoning, if necessary.