Heat olive oil in a large pot over medium heat.
Add Italian sausage and cook until browned, breaking it up as it cooks into small crumbles.
Remove cooked sausage and add mushrooms to the pan. Cook until mushrooms release their liquid and are nice and soft.
Add diced celery and onion and cook until onions are translucent and celery is soft.
Return cooked sausage to the pan and add sliced pepperoni.
Add diced tomatoes and chicken broth. Stir to combine.
Add garlic powder, salt, pepper, Italian seasoning, rosemary, and red pepper flakes.
Increase heat and bring soup to a simmer.
Stir in tortellini. Simmer until tortellini are cooked al dente, about 5-8 minutes.
Gently stir in spinach leaves and red bell pepper.
Stir and continue to cook until spinach wilts.
Place oven safe soup bowls on a cookie sheet and ladle soup into individual bowls.
Top each bowl of soup with grated Parmesan cheese.
Add a slice of Mozzarella cheese to each bowl of soup.
Place bowls in the oven and set oven temperature to broil. Heat under broiler until cheese is melted and starts to brown.
Serve with garlic breadsticks.