Remove the turkey from the refrigerator about 1 hour before roasting, while you make the stuffing.
Arrange the racks in the oven so the turkey will fit on the middle shelf. Preheat the oven to 450°F (230°C).
Rinse the turkey under cold water. Remove the neck, gizzard, and heart and set aside to make the gravy. Remove the liver and save for another use. (The liver is delicious lightly coated in flour and then sauteed with 1 teaspoon butter in a skillet over medium-high heat for 5 to 6 minutes per side.) Pat the turkey dry with paper towels.
Use the vegetable oil to lightly grease the bottom of a large roasting pan. Season the turkey with salt and pepper, inside the cavity and on the outside.
Loosely stuff both the body and neck cavities of the turkey with the stuffing, pressing down but being careful not to overstuff the turkey. Press the slice of bread into the cavity at the wide opening to keep the stuffing inside so it won't fall out while the turkey roasts. Place the turkey in the roasting pan, breast side up.
In a medium skillet, heat the butter over low heat. Add the garlic cloves and cook for 5 minutes, until the butter has completely melted and the garlic is just beginning to turn light golden brown. Remove from the heat.
Using a spoon or a barbecue or pastry brush, brush the skin of the turkey with some of the garlic butter, reserving the rest to baste with later, and scatter at least half the garlic cloves around and on top of the turkey. Sprinkle the top of the turkey with the paprika.
Using a piece of kitchen string, tie the legs together to keep them from touching the sides of the roasting pan. (Tying the legs also makes for a "neater"-looking roasted turkey.)
Place the pan in the oven and roast for 15 to 20 minutes per pound, depending on the freshness of the turkey, or 2 hours 30 minutes to 3 hours 20 minutes for a 10-pound turkey or 3 hours 45 minutes to 5 hours for a 15-pound turkey. (Fresh turkey tends to cook much faster than those that have been frozen.) After 30 minutes, reduce the heat to 350°F (175°C). Baste the turkey every hour or so with the remaining garlic and butter and with the liquids that have accumulated on the bottom of the roasting pan.
When you've estimated that the turkey has about 1 hour remaining to roast, place the carrots, parsnips, and onions in a bowl and season with salt and pepper. Scatter the vegetables around the turkey. (If there isn't a lot of room left in your roasting pan, place the vegetables in a well-oiled baking pan and place on the rack below the turkey.)
Roast for 1 hour, stirring the vegetables once or twice so they brown evenly on all sides. If the turkey skin appears to be browning too quickly, cover the turkey very loosely with aluminum foil.
Test for doneness. The turkey should be a gorgeous golden brown; when you wiggle a drumstick it should feel slightly loose; an instant read thermometer inserted into the thickest part of the thigh should read between 170°F and 180°F (76°C and 82°C), and when you pierce the skin directly above the wing the juice should run clear yellow, not pink. Gently remove the turkey from the roasting pan and place on a serving platter; cover loosely with aluminum foil.