Preheat oven to 450ºF.
Rub outside of chicken with 1 tablespoon oil; season with a few pinches of salt.
Stuff cavity with rosemary. Lightly squeeze orange pieces to release juices and place in cavity.
Scatter vegetables in a roasting pan. Toss with remaining oil and season with salt and pepper. Place chicken on top of vegetables breast side up.
Roast for 30 minutes; then lower oven temperature to 350ºF and cook for 30 to 45 minutes longer, or until a thermometer inserted into the thigh reads 165ºF.
Remove from oven and let rest for 20 minutes before slicing. Serve with roasted vegetables and pan juices.