Peel first 5 ingredients, and cut into large pieces. Coat 2 aluminum foil-lined baking sheets with cooking spray. Arrange parsnip, turnip, sweet potato, and rutabaga on a baking sheet. Lightly coat vegetables with cooking spray, and sprinkle with 3/4 teaspoon salt and 3/4 teaspoon pepper.
Arrange beets on remaining baking sheet; lightly coat with cooking spray, and sprinkle with remaining 1/4 teaspoon salt and 1/4 teaspoon pepper.
Bake vegetables at 425°, stirring occasionally, 35 to 45 minutes or until tender. (Pans may need to be rearranged after 15 to 20 minutes to ensure even cooking.)
Toss vegetables with melted butter.
Note: We cooked the beets separately to keep them from bleeding into the other vegetables.