01 - Preheat the oven to 375°F. Lightly grease a 9x13-inch baking dish with butter or nonstick spray.
02 - Boil the lasagna noodles according to package directions until al dente. Drain, rinse briefly with cool water, and lay each noodle flat on a clean baking sheet or parchment paper to prevent sticking.
03 - In a large mixing bowl, combine the shredded chicken, ricotta, mozzarella, Parmesan, minced garlic, parsley, egg, salt, and pepper. Stir until evenly incorporated.
04 - Melt the butter in a medium saucepan over medium heat. Whisk in the flour and cook for 1 minute to form a roux. Gradually pour in the milk while whisking constantly. Continue cooking and whisking until the sauce thickens, about 3 to 4 minutes. Stir in the Parmesan and garlic powder, then season with salt and pepper to taste. Remove from heat and set aside.
05 - Spread 1/2 cup of marinara sauce evenly across the bottom of the prepared baking dish. Lay each cooked noodle flat and spread approximately 2 to 3 tablespoons of the chicken filling along its length. Roll each noodle up tightly and place seam-side down in the dish.
06 - Pour the creamy Parmesan sauce over the roll ups, followed by the remaining marinara sauce. Sprinkle the mozzarella and Parmesan cheeses evenly over the top.
07 - Bake uncovered for 30 to 35 minutes, until the cheese is melted, bubbly, and lightly golden on top. Let rest for 5 to 10 minutes before serving.