Preheat oven to 400 degrees.
Slice beets and turnips into 1/8 inch slices and lay on a baking sheet with parchment paper. Brush the slices with butter or oil and sprinkle with salt and pepper.
Bake at 400 for about 10 minutes and then flip all the slices over. Continue baking for about another 10 minutes, until they are brown around the edges and tender in the center.