Heat a large soup pot/Dutch oven over medium high heat. Brown sausage and onions for 4 minutes, while breaking up sausage. Add bell peppers, garlic and red pepper flakes and sauté an additional 2-3 minutes or until meat is cooked through and onions are tender. Dain grease. Add all remaining soup ingredients except cheeses.
Cover the soup and bring to a boil. Once boiling, reduce heat to LOW and continue to simmer, covered, stirring occasionally and replacing the lid for 8-12 minutes or until rice is cooked. ***NOTE: Cooking time may vary depending on your rice and how long it takes to bring your soup to a boil so I suggest checking the rice occasionally until done.
Stir in Parmesan cheese and season with salt and pepper to taste (I add a pinch more salt). Stir in additional broth if desired for a thinner soup.
Ladle soup into bowls and top with freshly shredded mozzarella. Dig in!