Preheat oven to 220C. Lightly grease a roasting pan. Place a wire rack into roasting pan. Trim excess fat from chicken. Discard neck. Rinse chicken (including cavity) under cold running water. Pat-dry with paper towels. Season cavity with salt and pepper.
Put some butter or margarine into a cup, place in microwave and melt, brush over chicken skin Or Gently squeeze the juice from half the lemon over chicken, rubbing juice into skin. Place both lemon halves into chicken cavity. Tie legs together with kitchen string.
Brush both sides of chicken with oil. Season chicken all over with salt and pepper. Place, breast-side up, onto rack in roasting pan. Roast for 1 to 1 1/2 hour or until juices run clear when chicken thigh is pierced with a skewer. Stand, covered, for 10 minutes. Serve, drizzled with pan juices and roast vegetables, if desired.