Wash and trim the roots, green leaves, or stalks. Cut them in halves in even pieces.
Spread the radishes on a sheet pan, and season them with Italian seasoning, salt, and pepper. Toss with olive oil, and make sure that the radishes are well coated.
Arrange in a single layer so that they crisp up. If the sheet pan is too crowded, the radishes will steam rather than roast.
Roast at 430°F/220°C for 20 minutes. If your radishes are big in size, they might take a bit longer so start checking after 15 minutes and flip them.
When they're crisp enough, take them out and serve them warm or at room temperature.
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Notes
Bigger radishes might take longer to roast. Start checking after 15 minutes, and flip them to evenly roast them.