Preheat oven to 425 degrees F. Place radishes in a 15x10-inch baking pan. Drizzle with 1 Tbsp. of the oil; toss to coat. Roast 30 to 35 minutes or until tender and light brown, stirring once.
Meanwhile, remove 1/2 tsp. zest and squeeze 1 Tbsp. juice from orange. For vinaigrette, in a small screw-top jar combine orange zest and juice, vinegar, honey, and remaining 2 Tbsp. oil. Cover and shake well. Season to taste with salt and pepper. Drizzle vinaigrette over radishes.