Preheat the oven to 400 degrees F.
Prepare the chicken by patting it dry with paper towels and removing the giblets and/or gravy pouch.
Sprinkle chicken with salt and pepper. Place lemon and rosemary in the cavity. Tie chicken’s legs together with kitchen twine. Spread butter over the top of the skin.
Place chicken in a roasting pan or a 9-x-13-inch baking dish.
Bake for 60 minutes, then check the temperature in the thickest part of the thigh. Continue cooking, checking every 10 minutes, until it reaches 165 degrees F.
Remove chicken from the oven and let it sit 10–15 minutes before cutting and serving.