Preheat the oven to 375°F/190°C.
Season the chicken cavity with salt and pepper, then stuff with half the onion, celery, and one sprig of rosemary. Truss the legs with kitchen twine if desired.
Drizzle half of the oil all over the chicken, and season it with salt and pepper (season liberally).
Add the remaining vegetable oil to the dutch oven so it covers so it lightly covers the bottom. Add the potatoes, remaining onions and celery, carrots and broth to the dutch oven. Season with salt, and give them a quick stir. Throw the remaining sprigs of rosemary in the dutch oven.
Transfer the chicken to the dutch oven so it sits over the chopped vegetables, cover with the lid.
Transfer the dutch oven to the oven and bake for 45 minutes.
Remove the dutch oven from the oven, remove the lid, and cook for 30 more minutes UNCOVERED or until the internal temp reaches 165°F/74°C (use kitchen thermometer). For crispy skin, place under the broiler for 3-5 minutes if desired.
Allow the chicken to rest for 10 minutes before carving.