Preheat oven to 400F and grease a baking dish or line it with parchment paper.
Wash, trim and halve radishes. Pat them dry. Place the radishes in a large bowl and toss them with olive oil and season with salt and pepper. Transfer them to the baking dish and arrange in a single layer. Roast radishes for 30 minutes or until golden and fork tender.
Meanwhile, make the vinaigrette by combining all of the ingredients in a jar with a secure lid. Shake until the dressing is emulsified. Taste and adjust seasonings to suit personal preference.
Before serving, drizzle the radishes with as much vinaigrette as desired and toss to coat evenly. Sprinkle with fresh parsley and serve.
Nutritional information includes the vinaigrette. Nutritional values will change if the vinaigrette is omitted.