Remove your turkey from the refrigerator and allow it to come to room temperature for 2 hours. Preheat your oven to 425°F.
Remove 2 tablespoons of ranch seasoning from one packet and reserve. In a small bowl, mix together 1 stick of butter with remaining ranch seasoning until well incorporated. Put cut vegetables into the bottom of a roasting pan, then the roasting rack. Put your turkey onto the rack (be sure you remove the giblets from the cavity if they are still in there). Spread the butter all over and underneath the skin of the turkey. Season generously with salt and pepper. Reduce oven temperature to 350°F and put the turkey inside.
In the meantime, add 2 cups of chicken stock to a saucepan along with the 2 tablespoons reserved ranch seasoning. Bring to a simmer just to warm through and incorporate the seasoning. Base the turkey with this liquid every 20 minutes until cooked through. * Remove the turkey when a thermometer inserted in the thickest part of the thigh reads 160°F. Tent with a piece of aluminum foil and rest at least 30 minutes. (There will be carryover cooking and the temperature will rise to 165°F while resting.)
For the gravy: Strain the juices left in the bottom of the roasting pan into a fat separator and pour the fat off the top. Put the roasting pan onto the burner of the stove over medium heat. Add 2 tablespoons butter and whisk in 3 tablespoons flour, cooking for a minute. Slowly whisk in the remaining 2 cups chicken stock along with any remaining braising liquid and the juices from the roasting pan. Season with salt and pepper and serve along side your turkey.
For safe meat preparation, reference the USDA website.