Preheat the oven to 350° F.Heat the olive oil in a large pot over high heat. When the oil shimmers, add the chicken sausage (if using) and brown all over, about 5 to 8 minutes. Stir in the garlic, oregano, thyme, fennel, and chili flakes, cook another 3-5 minutes, until very fragrant. Add the marinara sauce, vodka, pesto, and a pinch each of salt and pepper. Then add 2 1/2 cups water and the pasta. Increase the heat to medium-high. Bring the mixture to a boil. Stir frequently until the pasta is al dente, about 8-10 minutes. If needed, transfer the pasta to a baking dish. Top with the cheeses, then pepperoni. Sprinkle the basil over top.Transfer the baking dish to the oven and bake 20-25 minutes or until the cheese has melted and is lightly browned on top. Cool 5 minutes before serving. Serve with fresh rosemary. Enjoy!