Heat olive oil in a large pot over medium-high heat. Break sausage into chunks into pot.
Let brown on bottom about 3 minutes, then turn and break up sausage and cook until no longer pink. Transfer to a paper towel lined plate, leave rendered fat in pot over medium-high heat.
You should have about 1 Tbsp fat in pot, if needed add a little more olive oil or drain off some excess fat if there's too much.
Add onions, carrots and bell pepper and saute until starting to soften, about 6 minutes. Add garlic and saute 1 minute longer.
Pour in broth, tomatoes and add Italian seasoning. Return sausage to pot and season mixture with pepper to taste.
Bring to a simmer then cover, reduce heat to medium-low and let simmer 20-25 minutes.
While mixture simmers, prepare and cook a small shell pasta in a separate pot.
Remove from heat. Stir in spinach and let stand for 5 minutes.
Add desired amounts of pasta to soup.
Serve warm, topping servings with grated parmesan, or cilantro or chopped green onion.