Bring 2 quarts of cider, 1 cup of salt, soy sauce, black peppercorns, garlic cloves, ginger and rosemary to a boil in a very large (16-quart) pot, stirring to dissolve salt and sugar. Let cool to room temperature. Stir in 1 1/2 gallons of cold water. Add turkey to brine and press down to submerge. Cover and refrigerate overnight.

Remove turkey from brine and pat dry with paper towels; discard brine. Season lightly inside and out with salt and pepper. Place turkey, breast side up, on a rack set in a large heavy roasting pan, stuff with oranges and tie legs together with kitchen twine. Let stand at room temperature for 1 hour.

Preheat oven to 375 degrees. Combine the remaining 1 cup of cider and 3 cups of water in a roasting pan. Brush turkey with butter. Flip breast side down.

Roast turkey, breast side down, basting occasionally, for 1 hour. Using paper towels, flip turkey. Roast, basting occasionally, until an instant-read thermometer inserted into thickest part of thigh registers 165-degrees, 1–1 1/2 hours longer. Transfer turkey to a platter. Let rest for at least 20 minutes before carving.

Meanwhile, strain the juices from the roasting pan into a saucepan. Simmer over medium heat until juices have thickened, about 10 minutes. Serve the cider jus alongside the turkey.