In your large saucepan over high heat, drizzle in the olive oil and add both kinds of sausage (after cutting down the length and removing casings) with the diced onion. Cook, breaking up the sausage with a spatula, until the sausage is browning and the onion is translucent (about 5‑7 minutes). Then stir in the oregano, thyme and rosemary and cook for about a minute more.

Pour in the marinara sauce along with 1 cup of water for each jar (two jars total), stir well and bring to a simmer. Reduce heat to medium‑low and let it simmer, stirring occasionally, for one hour. Taste and adjust seasoning, and skim off any excess fat from the surface at the end.

While the sauce simmers, bring a large pot of generously salted water to a boil and cook the ziti about 1‑2 minutes less than the package directions (about 8 minutes) so it’s a little underdone. Drain well and transfer to a large mixing bowl. Then add the meat sauce and stir everything until combined. Let it rest for 5 minutes. Preheat your oven to 375 °F (190 °C) and grease a 9 × 15‑inch baking dish with a drizzle of olive oil (if using a 9×13 dish, reserve about a cup of cooked pasta to avoid overfilling).

Use a slotted spoon to transfer half the pasta‑sauce mixture into the prepared dish and smooth it into an even layer. Top with half the ricotta, half the mozzarella cubes, and half the grated Pecorino Romano evenly. Then add the remaining pasta‑sauce mixture, give the dish a little shake to settle it, and top with the remaining cheeses. Bake in the center of the preheated oven for about 30‑35 minutes, until the cheese is melted and the casserole is piping hot. Remove and let it cool for 10‑15 minutes before serving; sprinkle chopped parsley on top.