Preheat oven to 400˚F. Line a baking tray with parchment paper.
Wash and dry radishes. Cut off tops and bottoms, and cut large radishes in half lengthwise.
On parchment lined baking tray, toss radishes with oil. Sprinkle with Italian dressing mix (or garlic powder and Italian seasoning), pepper, and salt. Spread evenly in a single layer.
Roast radishes 25-30 minutes, until cooked to desired doneness, stirring after 15 minutes. Sprinkle with parsley.
Serve immediately or at room temperature. Serve with sour cream if desired.