While we think the roasted arugula chips are best fresh from the oven, you can wash and prep your leaves ahead of time. Once dry, store them in an airtight container in the refrigerator until you're ready to use them. If you do save some of your arugula chips and find they aren't as crisp, toss them in the oven at a low temperature for a few minutes to remove any excess moisture and re-crisp.