Rinse turkey, pat dry, and cut off drumsticks and thighs.
Mix salt and rosemary together in a small bowl. Sprinkle all over turkey pieces, including inside the cavity. Put all pieces in a roasting pan, slide into a large plastic bag, and loosely tie top. Chill at least 1 day and up to
Let turkey sit at room temperature 1 hour. Remove top rack of oven and preheat to 350°. Pat turkey dry with paper towels. Cover breast with pancetta (keep slices in their circle shapes and overlap slightly), then sprinkle with pepper. Rub wings with a bit of canola oil and set turkey carcass with breast on a V-rack in a large roasting pan.
Roast turkey carcass until an instant-read thermometer, inserted straight down through the breast until it touches bone, registers 160°, 2 to 2 1/2 hours. Tent carcass with foil after 45 minutes to keep pancetta from burning.
Heat 1 tbsp. canola oil, meanwhile, in a 12-in.-wide frying pan with at least 2-in. sides or in a wide stockpot over medium-high heat. Add turkey legs and thighs, skin side down, in a single layer and let cook undisturbed until skin is deep golden brown, 8 to 10 minutes. Turn over and brown 4 minutes.
Put turkey legs and thighs on a plate. Reduce heat to medium and pour off all but 1 tbsp. fat from pan. Add carrots, celery, onion, and giblets, if using, and cook, stirring occasionally, until softened and lightly browned, 7 minutes. Add bay leaf. Return legs and thighs (and juices) to pan, skin side up, and pour in enough stock to come halfway up turkey. Cover pan; reduce heat to low. Cook until an instant-read thermometer inserted in thickest part of a thigh registers 160°, 50 minutes to 1 hour.
Transfer legs and thighs to a rimmed baking sheet, skin side up; cover with foil. Strain stock through a fine-meshed sieve, discarding solids, and use to make gravy.
Remove turkey from oven and let rest 20 minutes. Meanwhile, put top rack back in oven, increase heat to broil and broil legs and thighs until skin is crispy, 10 minutes. Transfer to a warmed serving platter.
Cut each breast half from the carcass in one piece, slicing on either side of breastbone and as close to the bone as possible. Make a horizontal cut just above wing joint to release bottom part of each breast half; then cut off wings. Transfer meat to platter.
Note: Nutritional analysis is per serving with 2 tbsp. gravy.