Two to three days before roasting, thaw the turkey in the refrigerator or in a cooler at no more than 38ºF.
Combine the vegetable broth, salt, sugar, peppercorns, allspice, and ginger in a large stockpot and bring to a boil over medium-high heat. Stir until the salt and sugar dissolve. Remove from the heat. Cool the brine to room temperature, then refrigerate.
The eve before roasting, combine the brine, cold water, and ice in a cooler. Place the thawed turkey (guts, neck, and whatnot removed) breast-side down in the brine. Seal up the cooler and use it as an ottoman. Target brine time: 12 hours; flip the bird once about halfway through.
Roasting day: Heat oven to 500ºF.
Remove the bird from the brine and rinse inside and out. Discard the brine.
Place the bird on a roasting rack and place the rack inside a roasting pan. Pat the bird dry inside and out with paper towels. Allow the bird to sit at room temperature for at least 1 hour.
Combine the apple, onion, cinnamon, and water in a microwave-safe bowl. Microwave on high for 5 minutes. Drain and add to the turkey's cavity, along with the rosemary and sage. Truss, if you like. Lightly coat the bird with canola oil. Tuck the wings. Roast the bird on the lowest rack of the oven for 30 minutes.
Insert a probe thermometer into the thickest part of the breast and reduce the oven temperature to 350ºF. Roast until the thermometer registers 155ºF, about 2 1/2 hours.
Remove the bird from the oven, cover loosely with aluminum foil, and let rest at least 15 minutes before carving.