In a small roasting pan or baking dish, toss carrots, celery, and onion with 2 tablespoons olive oil, salt and pepper and place into the bottom of the pan.
Pat entire chicken dry with paper towels, add garlic bulb into the cavity of the bird and tie legs together with kitchen twine (or use a small rubber band). Brush with remaining 2 tablespoons olive oil and sprinkle generously with salt and pepper. Place overtop veggies and roast 60-90 minutes or until golden brown and registers at 165 degrees in the thigh.
Remove from oven, cover with foil and rest chicken 20 minutes. Carve the entire bird and serve.