Cook the noodles. Boil lasagna noodles in salted water until just shy of al dente. They should be pliable but not mushy.
Drain, rinse with cool water, and lay flat on a lightly oiled baking sheet to prevent sticking.
Make the Alfredo. In a saucepan, melt butter over medium heat. Add minced garlic and cook 30–60 seconds until fragrant. Whisk in flour and cook 1 minute.
Slowly whisk in half-and-half. Simmer, whisking, until slightly thickened, 3–5 minutes. Off the heat, stir in Parmesan and nutmeg.
Season with salt and pepper.
Prep the filling. In a bowl, combine chicken, 1 cup mozzarella, ricotta, 1/2 cup Parmesan, egg, parsley, and garlic powder. Season with salt and pepper. Mix until evenly combined.
Preheat and prep dish. Heat oven to 375°F (190°C).
Lightly grease a 9x13-inch baking dish. Spread about 1/2 cup Alfredo sauce across the bottom to create a thin layer.
Assemble the rolls. Spread 2–3 tablespoons of filling evenly over each noodle, leaving a small border at the edges. Roll each noodle up from the short end.
Place seam-side down in the prepared baking dish.
Sauce and cheese. Spoon the remaining Alfredo sauce over the rolls. Sprinkle with the remaining 1 cup mozzarella and a little extra Parmesan.
Bake. Cover loosely with foil and bake 15 minutes. Remove foil and bake another 10–12 minutes, until the cheese is melted and bubbling and the centers are hot.
Rest and serve. Let the rolls rest 5–10 minutes so they set slightly.
Garnish with parsley and serve warm.