In small bowl, combine lemon rind, garlic, salt, and pepper. Rub mixture over surface of pork.
Place pork in uncovered roasting pan; top with rosemary sprig. Roast 30 minutes. Turn roast over and baste with pan drippings; roast 30 minutes longer or until pork is done (170 degrees F on meat thermometer).
Let pork stand 15 minutes on cutting board. Cut pork into very thin slices; serve warm or at room temperature.