Preheat oven to 425°F (220°C). Pat the chicken dry with paper towels to help the skin crisp.
Rub the chicken all over with olive oil or butter. Season generously with salt, pepper, and dried herbs, including inside the cavity.
Stuff the cavity with garlic cloves and lemon halves if using.
Place potatoes, carrots, and onion in the roasting pan. Toss with a little oil, salt, and pepper.
Set the chicken breast-side up on top of the vegetables or on a rack.
Roast uncovered for 75–90 minutes, or until a thermometer inserted into the thigh reads 165°F (74°C).
Remove from oven and let rest for 10–15 minutes before carving.
Serve carved chicken with roasted vegetables and pan juices.