Place 1 sheet of phyllo dough on a 15x12-in. piece of waxed paper; brush with butter. Place a second phyllo sheet on top, brushing it with butter. (Keep remaining phyllo covered with a damp towel to prevent it from drying out.) Sprinkle with 1/4 cup walnut mixture. Using waxed paper, roll up tightly jelly-roll style, starting with a long side, removing paper as you roll. Slice roll into 4 smaller rolls; transfer rolls to a greased 13x9-in. baking dish. Repeat with remaining phyllo dough and walnut mixture, by 1/4 cupfuls. Bake until light brown, 14-16 minutes. Cool dish on a wire rack.