Heat the olive oil in a large pot over medium heat.
Add the chopped onion, diced carrots, and diced celery. Cook, stirring occasionally, until the vegetables are softened, about 7 minutes.
Add the minced garlic, dried thyme, dried rosemary, and crushed red pepper flakes. Cook for 1 minute until fragrant.
Pour in the vegetable broth, then add the drained cannellini beans, diced tomatoes with their juice, and the bay leaf. Stir to combine.
Bring the soup to a boil, then reduce heat to low and simmer uncovered for 30 minutes, stirring occasionally.
Remove the bay leaf. Using an immersion blender, partially blend the soup to your desired consistency, leaving some beans whole for texture. Alternatively, transfer half the soup to a blender, puree, and return to the pot.
Season with salt and freshly ground black pepper to taste.
Stir in the chopped spinach and cook for an additional 5 minutes until the spinach is wilted.
Remove from heat and stir in the chopped fresh parsley.
Serve hot, topped with grated Parmesan cheese if desired.