Root vegetables have a low-water content and freeze beautifully compared to bell peppers, zucchini and tomatoes which have a high-water content. After roasting, cool them completely in a single layer on a clean baking sheet. Flash freeze by placing the pan in the freezer for 2-4 hours to keep them from sticking together then transfer into resealable freezer bags. Bake from frozen at 400 degrees F for 20-30 minutes until hot and crispy.