Preheat oven to 350 degrees.
Peel and thinly slice the root vegetables on a mandolin. I would suggest slicing the beet last so that the beet doesn't stain or bleed over the other vegetables.
Arrange the thinly sliced vegetables in circles in a cast iron skillet, or other round oven-safe dish.
When the skillet is full of vegetables, drizzle with olive oil, dot with butter, and sprinkle with cheese and thyme.
Bake for about 40-45 minutes, or until all of the vegetables are fork tender.