Preheat oven to 350˚. Snap off tough ends of asparagus and cut into 1-inch pieces; arrange in a steamer basket over boiling water. Cover and steam 6 minutes or until crisp-tender. Plunge asparagus into ice water to stop cooking process; drain and set aside. In a large saucepan, bring about 1 quart of water to a boil; add shrimp and cook 3 to 5 minutes, or just until they turn pink. Drain and rinse with cold water. Peel shrimp and devein, if desired. Set aside.
Melt butter in a heavy saucepan over medium heat; add scallions and cook 2 minutes, stirring constantly. Whisk in flour; cook 1 minute, whisking constantly. Gradually whisk in milk; cook, whisking constantly, until mixture is thickened and bubbly. Whisk in salt, pepper, dill, and ½ cup Parmesan cheese. When blended, reserve 1 cup of sauce to use later. Then stir shrimp and asparagus into remaining sauce.
Spoon about ¼ cup filling down the center of each crepe. Roll up and place seam-side down in a lightly greased 13x9-inch baking dish. Spoon remaining 1 cup sauce over crepes; sprinkle with remaining ¼ cup Parmesan cheese. Bake 20 minutes or until thoroughly heated.