Preheat oven to 450°. Remove the neck and giblets from the chicken, and reserve for another use. Rinse the chicken with cold water, and drain the cavity well. Pat dry with paper towels. Sprinkle 1/2 teaspoon salt inside cavity. Place lemon half inside the cavity.
Stir together the pepper, rosemary, and remaining 1 teaspoon salt. Brush the outside of the chicken with oil. Rub 2 1/2 teaspoon of the pepper mixture into the skin. Sprinkle the remaining pepper mixture over both sides of the breast.
Place chicken, breast side up, on a lightly greased wire rack in a lightly greased shallow roasting pan. Add 3/4 cup water to the pan.
Bake at 450° for 20 minute. Reduce the heat to 375°, and bake for 30 minutes. Baste the chicken with the pan juices; drizzle with melted butter. Bake 15 to 25 minutes or until a meat thermometer inserted in the thigh registers 165°, shielding with aluminum foil to prevent excessive browning, if necessary. Remove the chicken from the oven, and baste with pan juices. Let stand 10 minutes before slicing.