We've done this a number of times in mid-summer when the radishes are really coming on:
2 bunches medium radishes (such as red, pink, and purple; about 20)
1 1/2 tablespoons olive oil
Coarse kosher salt
2 tablespoons (1/4 stick) unsalted butter
1 teaspoon fresh lemon juice
Preparation
Preheat oven to 450°F. Brush large heavy- duty rimmed baking sheet with olive oil. Cut off all but 1/2 inch of green radish tops; reserve trimmed tops and rinse them well, checking for grit. Coarsely chop radish tops and set aside. Cut radishes lengthwise in half and place in medium bowl. Add 11/2 tablespoons olive oil and toss thoroughly to coat. Place radishes, cut side down, on prepared baking sheet; sprinkle lightly with coarse salt. Roast until radishes are crisp-tender, stirring occasionally, about 18 minutes. Season to taste with more coarse kosher salt, if desired.
Melt butter in heavy small skillet over medium-high heat. Add pinch of coarse kosher salt to skillet and cook until butter browns, swirling skillet frequently to keep butter solids from burning, about 3 minutes. Remove skillet from heat and stir in fresh lemon juice.
Transfer roasted radishes to warmed shallow serving bowl and drizzle brown butter over. Sprinkle with chopped radish tops and serve. We've done the same thing with the longer "icicle" radishes as well and it works equally as well...
We sometimes add just a hint of garlic salt...