Preheat the oven to 350°F (175°C).
Cook the frozen cheese tortellini according to the package directions for about 3 minutes. Drain well.
Meanwhile, cook the beef Italian-style sausage in a skillet over medium heat until browned and fully cooked, breaking it into crumbles. Drain any excess grease.
In a large bowl, combine the cooked tortellini, sausage, pasta sauce, Parmesan cheese, garlic powder, oregano, and basil.
Toss everything until evenly coated.
Grease an 8×8-inch casserole dish and transfer the mixture into an even layer.
Sprinkle the mozzarella cheese evenly over the top.
Cover with aluminum foil and bake for 20 minutes.
Remove the foil and broil for 2–3 minutes until the cheese is bubbly and lightly golden.
Garnish with fresh parsley before serving your delicious Italian Sausage Tortellini Casserole.