Italian Sausage Pasta with Vegetables

2 tablespoons olive oil
4 Italian sausages (1 pound), casings removed, sliced
1 small onion, very finely chopped
4 garlic cloves, finely minced
1 tablespoon Cajun seasoning
1 bell pepper, very finely chopped
4 medium tomatoes, chopped, or 15 cherry tomatoes, each sliced in half
8 ounces mushrooms, finely sliced
3/4 cup red wine
10 oz penne pasta (for gluten-free, use gluten-free brown rice penne, such as Tinkyada brand)
1/2 cup fresh Parmesan cheese, grated