Cook according to package directions until al dente. Drain, then lay flat on a rimmed baking sheet, spraying lightly with cooking spray.
In a large mixing bowl, combine butternut squash purée, ricotta, grated Parm, egg, chopped sage, Kosher salt, and black pepper. Stir until well mixed.
Melt unsalted butter. When melted, add all-purpose flour, whisk until the flour is a light golden brown. Whisk in warm milk. Bring to a simmer. Stir in grated Parm, grated nutmeg. Set aside.
Preheat oven. Lay out as many lasagna noodles as will fit. Place filling on each noodle to spread into a thin layer. Sprinkle each with shredded mozzarella. Roll each noodle.
Place the roll ups in the pan. Drizzle the remaining béchamel sauce all over the top. Sprinkle any remaining mozzarella cheese on top. Bake.
Sprinkle with grated Parm and black pepper, if wanted, then garnish with sage leaves and enjoy!