In a large pot over medium heat, heat oil. Add onions, carrots, garlic, Italian seasoning, and red pepper flakes and season with salt and pepper. Cook, stirring occasionally, until vegetables soften, about 6 minutes.
Add marinara and chicken broth and bring to a simmer. Add sausage meatballs and pasta and cook, stirring frequently, until pasta is al dente, 9 to 12 minutes. Stir in spinach to wilt and then remove from heat.
Serve with Parmesan.
