Spray two large non-stick baking sheets with cooking oil.
Using a mandoline, set to 1/16" inch, carefully slice sweet potatoes, or other root vegetable, thinly. *Note* If making beet chips, be sure to layer beet chips between paper towels and extract as much moisture as possible to ensure they crisp properly. Sweet potatoes do not need to be toweled.
Lay in a single layer onto baking sheet, and spray gently with non-stick spray or coconut oil spray. Sprinkle with sea salt, pepper, and lightly with minced rosemary.
Place in oven and bake for approximately 7-9 minutes. Remove from oven and let rest for 5 minutes. Place back into oven and continue to bake additional 5-7 minutes until chips are crispy and the centers are dry. Remove from oven, let cool and then devour.