Preheat oven to 375 degrees F (190 C) and place oven rack in the center of the oven.
Line two baking sheets with parchment paper.
Thinly slice beets with a mandolin, getting them as consistently thin as possible.
Divide between two baking sheets and spray or very lightly drizzle with olive oil.
Add a pinch of salt, pepper, and the rosemary. Toss to coat.
Arrange in a single layer, making sure the slices aren’t touching.
Bake for 15-20 minutes or until crispy and slightly brown.
Remove from oven. Let cool slightly. Then serve.
