Heat the olive oil in a large pot over medium heat. Add sausage and cook until browned, breaking it apart with a spoon, about 5-7 minutes. Drain excess fat.

Add chopped onions to the pot and cook until softened, about 7 minutes. Stir in garlic, oregano, red pepper flakes, and salt, cooking for an additional minute.

Stir in tomato paste and cook for 1 minute. Add diced tomatoes with juices, chicken broth, and bay leaves. Bring to a boil, then reduce heat, cover, and simmer for 30 minutes.

Increase heat to medium-high. Add uncooked pasta and cook until al dente, about 10 minutes. Remove bay leaves.

Stir in chopped basil. Season with salt and pepper to taste.

Serve hot, adding a spoonful of ricotta to each bowl, then topping with shredded mozzarella cheese.