Preheat oven to 400 °F. Toss the trimmed radishes with oil and spices. Arrange seasoned radishes in a single layer on a rimmed cookie sheet.
Roast for 30-35 minutes, until they appear golden and crispy.
An easy way to test for doneness is by sticking them with a fork. The radishes should have a crisp outside and tender inside, similar to a baked potato.