Preheat oven to 350°F. Brush oil over the bottom of a large, sturdy roasting pan. If you’re using a foil pan, place it on a heavy baking sheet.
Remove giblets from the turkey and make sure cavities are free of debris. Tuck wingtips under the bird and tie drumsticks together with kitchen twine. Dry the skin thoroughly. Coat the bird with 2 to 3 tablespoons olive oil.
Mix thyme, sage, garlic powder, salt and pepper together in a small container. Sprinkle 2/3 of this herb mixture over the bird. Place sprigs of rosemary inside the cavity.
Arrange root vegetables around the base of the bird, well inside the roasting pan. Drizzle remaining oil over vegetables and then sprinkle them with remaining herb mixture.
Place turkey in preheated oven and roast about 15 minutes per pound. Begin checking the internal temperature after 2 hours. Turkey is done when breast meat is 150°F and thigh meat is 165°F.
Remove turkey from oven and cover with foil. Let rest in a warm spot 20 to 30 minutes before carving. Garnish with fresh thyme or other herbs, cranberries and bay leaves, if desired.