Preheat oven to 425 degrees. Tie chicken legs together with kitchen twine (tuck wings under chicken, if desired, for a neater presentation). Place chicken on a rack set in a roasting pan (or on a rimmed baking sheet).
Rub chicken all over with butter; season with 1 teaspoon salt and 1/2 teaspoon pepper. Roast until an instant-read thermometer registers 160 degrees when inserted in the thickest part of a thigh (avoiding bone), 45 to 50 minutes. Serve, or let cool before refrigerating, up to 3 days, covered.