Slow Cooker Ratatouille with Sausage

Name: Slow Cooker Ratatouille with Sausage
Ingredients: 3 (4 ounce) links mild Italian sausage; 2 zucchini, sliced 1/4-inch thick; 2 yellow summer squash, sliced 1/4-inch thick; 1 medium eggplant, sliced 1/4-inch thick; 1 medium onion, chopped; 1 yellow bell pepper, chopped; 1/4 cup olive oil; 1/4 cup herbes de Provence; 2 teaspoons salt, or to taste; 1/2 teaspoon ground black pepper, or to taste; 1 (28 ounce) can crushed tomatoes; 1/4 cup grated Parmesan cheese, or to taste