Rub the chicken breasts all over with the salt and pepper. Let rest while the oven preheats to 450°F.
Lay the lemon slices and rosemary all over the bottom of a roasting pan and place the chicken on top, leaving space in between the breasts so they have room to crisp up. Drizzle generously with the oil.
Roast until the breasts are golden and done through and through, 25 to 30 minutes. Serve hot with the pan juices spooned all over the flesh.