Preheat your oven to 375°F (190°C). Grease a 9×13 inch baking dish or casserole dish.
In a large pot of boiling salted water, cook the tortellini according to package instructions until al dente. Drain and set aside.
In a large mixing bowl, combine the cooked tortellini, pizza sauce, sliced pepperoni, and half of the mozzarella cheese. If using, add the Italian seasoning, garlic powder, and red pepper flakes. Stir until everything is evenly coated.
Pour the tortellini mixture into the prepared baking dish, spreading it evenly. Top with the remaining mozzarella cheese and Italian cheese blend.
Bake in the preheated oven for about 20-25 minutes, or until the cheese is bubbly and golden brown.
Remove from the oven and let it cool for a few minutes. Garnish with fresh basil or parsley if desired. Serve warm.
