1 teaspoon chopped flat-leaf (Italian) parsley, or to taste
Method
Begin by assembling your ingredients. Slice the sausage links lengthwise and remove the casings.
In a large saucepan over high heat, warm some olive oil. Add the sausage and chopped onion, cooking and stirring until the sausage is browned and the onion is soft, about 5 to 7 minutes. Incorporate oregano, thyme, and rosemary, and cook for an additional minute.
Stir in the marinara sauce and add a cup of water to each sauce jar to clean out any remaining sauce. Mix well and bring the mixture to a gentle simmer.
Lower the heat to medium-low and let the sauce simmer for 1 hour, stirring occasionally. Taste and adjust seasoning if necessary. Once done, turn off the heat and set aside, skimming off any excess fat that appears on top.
While the sauce is simmering, bring a large pot of salted water to a boil. Add the ziti and cook for 1 to 2 minutes less than the package instructions, approximately 8 minutes. Drain carefully and put the pasta in a large mixing bowl.
Gently fold the meat sauce into the pasta until everything is well mixed. Allow it to rest for 5 minutes. Meanwhile, preheat your oven to 375°F (190°C) and lightly grease a 9x15-inch or 9x13-inch baking dish with olive oil.
Transfer half of the pasta and sauce mixture into the prepared baking dish, spreading it out evenly with a spatula. Layer half of the ricotta, mozzarella, and grated Pecorino Romano cheese on top. Then, add the remaining pasta mixture and gently shake the dish to settle it. Finish by layering the remaining cheese on top.
Bake in the preheated oven for 30 to 35 minutes, or until the cheese is bubbly and golden. Once done, let it cool for 10 to 15 minutes before serving. Garnish with fresh parsley.
