In a small bowl, mix all the ingredients together.
Store the dry rub in a container with a lid.
One day before roasting, rub the dry brine mixture all over the turkey, under the skin, and inside the cavity.
Place on rack in roasting pan with carrots, celery, and onions stuffed inside the turkey and spread under the rack in the pan.
Refrigerate rubbed turkey for 24 hours, uncovered.
One hour before roasting, remove the turkey from the refrigerator and let stand at room temperature.
Preheat the oven to 400℉ and tie the legs together with kitchen twine. Also, tuck the wings behind the neck and under the turkey.
Position turkey breast-side down on rack and roast turkey for 30 minutes.
Add 1 c. water (or broth, if using) to roasting pan and roast another 30 minutes.
Remove the turkey from the oven, and reposition breast-side up on rack. Return turkey to oven, and add additonal ½cup water (or broth). (Keep adding water/ broth as needed to keep vegetables in bottom of pan moist.)
Continue to roast turkey until instant-read thermometer inserted in thigh reads 170℉ (about another 45 minutes for 10-lb turkey, about another 1 hour for 12-lb. turkey, or about another 1½ hours for 17-lb. turkey).
Transfer turkey to a carving board or platter, tent with foil, and let rest for 45 minutes-1 hour before carving and serving.
Meanwhile, make gravy from the pan drippings.