1. Preheat oven to 375°. Stir together salt and pepper. If applicable, remove necks and giblets from chickens, and reserve for another use. Pat chickens dry.
2. Sprinkle 1/2 tsp. salt mixture inside cavity of each chicken. Place 2 lemon halves and 1 rosemary sprig inside cavity of each chicken. Rub 1 1/2 tsp. olive oil into skin of each chicken. Sprinkle with remaining salt mixture; rub into skin. Tuck chicken wings under, if desired. Lightly grease a wire rack in a 17- x 12-inch jelly-roll pan with cooking spray. Place chickens, breast sides up and facing in opposite directions (for even browning), on wire rack.
3. Bake at 375° for 1 1/2 hours or until a meat thermometer inserted in thigh registers 180°. Cover and let stand 10 minutes before slicing.