Rinse the white and cranberry beans in a sieve under running water. Dump them into the slow cooker and add the carrots, celery, potato, onion, garlic, rosemary, and
Turn the cooker to high. Fold in the bread and tomatoes. Season the soup with salt and plenty of pepper, cover, and cook until the bread and tomatoes have broken down somewhat and the bread has thickened the soup, about 15 minutes. Serve.