Heat oil in a large dutch oven or stock pot (at least 6 quarts) over medium heat. Add sausage to the pot, removing the casing if necessary. Use a spatula to break up the sausage and cook until done.
Add the onion, carrots, celery, salt and pepper to the pot. Cook about 5 minutes or until vegetables are softened, stirring well. Add tomato paste, fennel seeds, and oregano and cook for a minute, stirring well. Stir in garlic and cook for about a minute.
Add tomatoes with their juice to the pot. Use a spatula to break up the tomatoes into small bite size pieces and deglaze the pan. Stir well to combine.
Pour in the broth and bring to gentle boil. Add the parmesan rind to the pot if using.
Add frozen spinach, return to boil. Cover and cook for 8-10 minutes or cook according to instructions on frozen spinach packaging, stirring occasionally to break up spinach. Once spinach is cooked, stir well to combine.
Add beans with their liquid (if using canned beans), stir well to combine, and again bring back to simmer.
Add dried pasta. Bring to boil and cook for 8 - 10 minutes or until pasta is tender to your liking. Use timing on pasta package as a guide.
Remove parmesan rind and discard. Taste and add salt or pepper as you like. Garnish with grated Parmesan if desired.