In large soup pot on medium heat, brown sausages on stove top in oil. When they're golden on all sides remove to plate to cool (they're not fully cooked yet and will finish cooking in the broth). Lower heat and in the small amount of fat that remains in the pot, add onions and carrots, cover and sweat until softened (5-8 minutes). You don't want them to brown.
When softened and aromatic, add garlic, zucchini, squash, Old Bay Seasoning, salt, pepper and red pepper flakes. Stir to combine. While these are cooking (still on low temp), slice sausages into 1/4 to 1/2 inch rounds.
When sausages are sliced, add them along with broth, diced tomatoes, tomato sauce, water, bay leaves, oregano and ground cayenne to vegetables in soup pot. Increase heat until liquid comes to a near boil. Reduce heat, cover and simmer for 40 minutes. Add spinach and beans, cook 5 minutes and soup's ready. Top with parmesan.