Turn on the oven to preheat to 180 degrees. Grease two large baking sheets with vegetable oil.
Peel the sweet potatoes and beets and cut into slices, approximately 2 mm thick. Put on a paper towel in one layer, cover with a second towel, dry well.
Put the chopped root vegetables on baking sheets in one layer, grease them with vegetable oil on top (it is better to sprinkle with oil from a spray bottle). Sprinkle with salt and pepper.
Place the baking sheets in a preheated oven for 10 minutes. Remove the baking sheets from the oven, leave at room temperature for 5 minutes.
Place the trays back in the oven and cook the chips for about 4-8 minutes, changing the trays every minute after the first 4 minutes of cooking.
Put the fried chips on a paper towel, leave for 5 minutes.