1. Cook cabbage leaves in boiling water 3 to 4 minutes or just until tender. Drain.
2. Heat a large nonstick skillet over medium-high heat. Add onion; sauté 5 to 7 minutes or until tender. Remove pan from heat; stir in rice. Cool 15 minutes.
3. Combine rice mixture, pork, sausage, and pepper. Spoon about 1/4 cup mixture into center of 1 cabbage leaf. Fold in edges of leaves. Starting at stem end, roll up jelly-roll fashion. Repeat procedure with remaining leaves and filling.
4. Combine sauerkraut and caraway seeds. Spoon half of sauerkraut mixture into a 4-quart electric slow cooker coated with cooking spray. Top with half of cabbage rolls, seam sides down. Repeat layers with remaining sauerkraut mixture and cabbage rolls.
5. Combine tomato juice, brown sugar, and tomato paste, stirring with a whisk. Pour tomato juice mixture over cabbage rolls. Cover and cook on LOW for 6 hours. Serve rolls with sauerkraut mixture.