In a slow cooker, stir together the cod, tomatoes, clam juice, onion, celery, carrots, wine, parsley, rosemary, and salt. Cover, and cook on Low 7 to 8 hours or on High 3 to 4 hours.
One hour prior to serving, mix flour, butter, and light cream in a small bowl. Stir into the slow cooker until the fish mixture is thickened.