Place brautwurst in a 5- to 6-quart slow cooker. Toss together saurkraut, apples, onion, brown sugar and caraway seed; spoon over brautwurst.
Cover and cook on high setting 1 hour; reduce heat to low setting and cook 2 to 3 more hours, stirring occassionally. Fill rolls, using a slotted spoon. Serve with mustard on the side, if desired.