Brush fillets with melted butter; sprinkle with seasoned salt and pepper. Starting with a short side, roll up. Place seam side down in a greased 9-in. square baking pan. Pour 1/2 cup milk over fillets. Bake, uncovered, at 350° for 25-30 minutes or until fish flakes easily with a fork.
Meanwhile, in a small saucepan, melt butter. Stir in flour until smooth; gradually add remaining milk. Bring to a boil; cook and stir for 1 minute or until thickened. Reduce heat; stir in the cheese, sherry and tarragon.
Drain pan juices from fish, reserving 1/4 cup; stir into cheese mixture. Pour over fish; sprinkle with paprika. Broil 4 in. from the heat for 3-4 minutes or until lightly browned.