Heat a large skillet or wide Dutch oven over medium-high heat and drizzle with olive oil. Add the ground sausage and use a sturdy spatula to break up the sausage. Once the sausage becomes caramelized and begins browning, about half way halfway through the cooking, add the dried oregano and red pepper flakes, if using.
Continue cooking until the sausage is cooked through, then remove from the Dutch oven and set aside
While the sausage cooks, make the mirepoix. Add the carrot, celery and onion to a food processor and pulse until finely chopped and there are no large pieces left.
To the same Dutch oven, add the chopped mirepoix and cook the vegetables for 3-5 minutes to soften, then add the garlic and continue cooking for another 1-2 minutes. Add the tomato paste and use a spatula to break up the tomato paste into the vegetables and continue cooking for another minute.
Pour in the red wine and use a sturdy spatula to scrape up any meaty bits from the bottom of the skillet. Let the wine reduce for another 1-2 minutes.
Add the crushed tomatoes and ground sausage with any residual drippings back into the Dutch oven and season with salt and pepper. Give everything a good stir.
Place a lid over the top of the pot, leaving a small opening. Simmer the pork ragu for 30-45 minutes until the sauce thickens.
Once done, add the cooked rigatoni to the pork ragu and stir to combine so all of the sauce coats all of the pasta. Add ¼ cup of starchy pasta water as needed to loosen the sauce.
Serve the pork ragu garnished with grated Parmesan and fresh basil on top.