In a large stock pot on medium heat, add oil and brown sausage. Remove and set aside. Add onions, carrots, celery, salt, pepper, beans, rosemary sprig, chicken stock and Parmesan rind. Increase heat to medium-high, bring to a simmer, cover and cook for 15 to 20 minutes, until vegetables are tender.
Remove rind and rosemary sprig. Using an immersion blender, blend half of the soup, leaving it chunky. Add cooked sausage, spinach and chili flakes. Stir until spinach is wilted. Serve.