Preheat the oven to 230 C / Gas 8. Wash the chicken thoroughly and pat dry with kitchen paper.
Sprinkle salt on all sides of the chicken and inside the cavity. Sprinkle with pepper and half of the rosemary. Place the other rosemary sprig, whole, inside of the cavity along with the whole garlic cloves and lemon halves.
Place chicken on a roasting rack set over a roasting tin. Roast for about 1 hour in the preheated oven, or until juices run clear.