Heat the oven to 450ºF.
Meanwhile, trim the stem ends from 1 pound loose red globe radishes. Halve lengthwise; if they are small (less than 1-inch wide), leave whole.
Place the radishes in a large bowl, drizzle with 1 tablespoon olive oil, and season with ¾ teaspoon kosher salt, ½ teaspoon granulated sugar, and ¼ teaspoon black pepper. Toss to combine.
Transfer to a rimmed baking sheet and arrange the radishes cut-side down into a single layer.
Roast until knife-tender and the cut sides begin to brown, about 13 minutes.
Add 2 minced garlic cloves, toss to combine, and rearrange into a single layer (it’s OK if some radishes end up cut-side up).
Return to the oven and roast until the garlic is golden brown, 5 to 7 minutes more.
Garnish with 1 tablespoon finely chopped fresh parsley, dill, and/or chives right before serving.
