Bring a large pot of lightly salted water to a boil. Add pasta and cook according to packet directions; drain. Adjust oven rack to the highest position and preheat grill. Generously butter or grease a baking dish.
Bring marinara and Alfredo sauces along with spinach and 1 tablespoon of Italian herbs to a simmer over medium-high heat. Reduce heat to medium-low and simmer for 10 minutes. Stir cooked tortellini into sauce then pour into prepared baking dish. Sprinkle with Mozzarella cheese, Parmesan cheese and remaining 1 teaspoon Italian herbs.
Grill for a minute or two until cheese has melted and turned golden brown.