Preheat oven to 400 degrees.
Fill a large pot with water and a pinch of salt and bring to a boil. Once the water boils, add the tortellini and cook about 1 1/2 minutes. The pasta will continue to cook in the oven, so you want it to be al dente. *If you are using fresh cheese tortellini there is so need to boil it or cook it in advance.
In a medium sauté pan over medium heat, cook the Italian sausage and break it up into small pieces. Once it's lost its raw red color, add the greens and cook it until they wilt.
Add the marinara sauce and the chopped tomatoes and stir to combine. Taste for seasoning and add 1/4 teaspoon of salt, fresh ground pepper or red pepper flakes if needed.
Spread 1/2 cup sauce on the bottom of a 9x13 casserole pan. Add the drained tortellini and top with the remaining sauce. Stir the casserole a bit to get sauce distributed throughout the casserole. (You can also layer half the tortellini and half the sauce, but I find it easier and more efficient to just add it all at one time.) Make sure sauce is covering the top layer of tortellini; if not, push the tortellini down into the casserole otherwise the edges of the pasta will be crispy.
Top with the mozzarella and the parmesan and bake at 400 degrees in the middle of the oven for 25 minutes.
Sprinkle with a chiffonade of fresh basil and serve with extra Parmesan on the side.