Remove and discard leg truss from turkey. Pull off and discard any lumps of fat. Remove giblets and neck (they're often packed in neck or body cavity) and save for classic gravy. Rinse turkey inside and out; pat dry.
Fill body cavity loosely with rosemary sprigs, garlic, onion, and lemons; if they don't all fit, tuck remaining into neck cavity. Fold skin flap under to hold in place. In a small bowl, mix olive oil, chopped rosemary, lemon peel, and pepper. Rub mixture all over turkey.
Place turkey, breast up, on a V-shaped rack in a 12- by 17-inch roasting pan (or one that is at least 2 in. longer and wider than the bird). Insert a meat thermometer straight down through thickest part of breast to the bone. (If using an instant-read thermometer, insert when checking temperature.)
Roast in a 325° or 350° regular or convection oven until thermometer registers 160°. (See below for times and temperatures.)
Remove herbs and vegetables from cavities and save for other uses (see notes) or discard. Transfer turkey to a platter. Let stand in a warm place, uncovered, for 20 to 30 minutes, then carve. If thigh joints are still pink (common in an oven-roasted bird), cut drumsticks from thighs, place thighs in a baking pan, and bake in a 450° oven until no longer pink, 10 to 15 minutes, or put on a microwave-safe plate and cook in a microwave oven at full power (100%) for 1 to 3 minutes.
Nutritional analysis per 1/4 pound boned cooked turkey with skin, based on percentages of white and dark meat in an average bird.
Oven-roasted turkey: temperatures and times:
For a 10-13 lb. turkey (weight with giblets): Bake in a 350° oven for 1 1/2-2 1/4 hr.
For a 14-23 lb. turkey (weight with giblets): Bake in a 325° oven for 2-3 hr.
For a 24-27 lb. turkey (weight with giblets): Bake in a 325° oven for 3-3 3/4 hr.
For a 28-30 lb turkey (weight with giblets): Bake in a 325° oven for 3 1/2-4 1/2 hr.
Times are for unstuffed birds. A stuffed bird may cook at the same rate as an unstuffed one; however, be prepared to allow 30 to 50 minutes longer.