
Preheat the oven to 450°. Rub the chicken with 1 tablespoon of the olive oil. Season the chicken inside and outside with 3 teaspoons of the salt and 1 teaspoon of the black pepper. Stuff the chicken with 2 onion wedges, the halved garlic head and thyme sprigs. Rub the outside of the chicken with the chopped thyme, paprika and onion powder. Set aside.
Toss together the potatoes, carrots, remaining onion wedges, 1 tablespoon of the olive oil, 1/2 teaspoon of the salt and ½ teaspoon of the pepper in a 6-quart round Dutch oven. Pour in the chicken stock. Place the chicken, breast-side up, on top of the vegetables and cover the Dutch oven with the lid.
Roast the chicken, covered, for 35 minutes. Uncover and continue roasting until a thermometer inserted in the thickest part of the thigh registers 165°, 20 to 25 minutes. Broil on high until the chicken begins to brown, 1 to 2 minutes. Remove from the oven and let chicken rest for 15 minutes.
Serve the carved chicken with the roasted vegetables and pan drippings.