Heat the olive oil in a large pot or Dutch oven over medium-high heat.
Add the sausage and cook, breaking it apart with a wooden spoon, until browned and cooked through.
Stir in the diced onion and cook until softened, about 5 minutes.
Add the minced garlic and tomato paste, cooking for 1 minute until fragrant.
Pour in the chicken broth, crushed tomatoes, diced tomatoes, dried basil, dried oregano, and red pepper flakes.
Bring the soup to a simmer, then add the broken lasagna noodles.
Cook for 10-12 minutes, or until the noodles are tender, stirring occasionally to prevent sticking.
Remove from heat and stir in the shredded mozzarella until melted.
Ladle the soup into bowls and top each serving with a generous dollop of ricotta cheese and a sprinkle of fresh parsley.