For the turkey: Remove the turkey from the refrigerator 1 hour before roasting.
Combine the butter, sage, rosemary, thyme, and parsley in a food processor and process until smooth. Season with salt and pepper.
Preheat the oven to 450 degrees F.
Season the cavity of the turkey with salt and pepper and fill the cavity with half of the carrots, celery, and onion. Rub the entire turkey with herb butter and season liberally with salt and pepper.
Put 4 cups of the chicken stock in a medium saucepan and keep warm over low heat.
Place the remaining vegetables on the bottom of a large roasting pan. Put the turkey on top of the vegetables, put in the oven, and roast in the oven until lightly golden brown, 45 minutes. Reduce the heat to 350 degrees F and continue roasting, basting with the warm chicken stock every 15 minutes, until an instant-read thermometer inserted in the thigh registers 160 degrees F, about 2 to 2 1/4 hours longer. Remove the turkey from the oven, transfer to baking sheet and tent loosely with foil, and let rest 20 minutes before slicing.
For the sage gravy:
Strain the cooking liquid from the roasting pan into a medium saucepan (should be about 4 cups, if not, add more stock to make 4 cups). Add the neck, bring to a boil, add the sage leaves, remove from the heat, and let steep for 15 minutes. Remove the sage leaves.
Melt the butter in a medium saucepan over medium-high heat. Add the flour and cook for 1 minute. Add the wine and cook until reduced. Whisk in the stock and cook until thickened and smooth, about 5 minutes. Season with the salt and pepper and chopped sage.