Heat olive oil in a large deep skillet or Dutch oven over medium heat.
Add the Italian sausage, breaking it up with a spoon, and cook until browned and cooked through, about 5-7 minutes.
Add the diced onion to the skillet and cook until softened, about 3-4 minutes.
Stir in the minced garlic and cook for 1 minute until fragrant.
Pour in the crushed tomatoes and chicken broth, stirring to combine.
Add the dried oregano, dried basil, crushed red pepper flakes, salt, and black pepper. Stir well.
Add the dry ziti pasta to the pot and stir to submerge the pasta in the liquid.
Bring the mixture to a boil, then reduce heat to medium-low and cover.
Simmer for 15-18 minutes, stirring occasionally, until the pasta is cooked and most of the liquid is absorbed.
Remove the pot from heat and sprinkle the shredded mozzarella and grated Parmesan evenly over the top.
Cover the pot again and let it sit for 3-5 minutes until the cheese melts.
Garnish with fresh basil leaves if desired and serve hot.