@webmd: Watch how @seasaltandkale turns frozen veggies into roasted deliciousness! How to Roast Frozen Veggies: Place your frozen veggies on a prepared baking sheet and pop them in the oven at 375°F with nothing on them for ~15 minutes. Then, take them out and toss with oil and preferred seasoning. Increase your oven temperature to 425°F and pop them back in for 20-25 minutes, or until roasted to your liking. Enjoy!