Cut a lengthwise slit down center of tenderloin to within 1/2 in. of bottom; open so meat lies flat. Cover with plastic wrap; flatten to 1/2-in. thickness. Remove wrap; sprinkle meat with salt and pepper.
In a small bowl, combine the apple, bread crumbs, celery, onion, raisins, walnuts and nutmeg. Sprinkle with 1 tablespoon apple juice; toss to coat. Spoon over pork. Roll up jelly-roll style, starting at a long side; tie with kitchen string and secure ends with toothpicks.
Place on a rack in a shallow roasting pan coated with cooking spray. Drizzle with 1-1/2 teaspoons apple juice. Bake, uncovered, at 375° for 30 minutes. Brush with remaining apple juice. Bake 20-25 minutes longer or until meat juices run clear and a thermometer reads 160°. Let stand for 5 minutes before slicing.
Meanwhile, in a small saucepan, combine cornstarch and cinnamon. Gradually whisk in apple juice until smooth. Bring to a boil; cook and stir for 1-2 minutes or until thickened. Serve with pork.