Preheat your oven to 450 degrees Fahrenheit. Line a baking sheet with parchment paper. Twist the greens off the radishes, put the greens into a bowl, and toss them with ½ teaspoon of the oil.
Cut the radishes in half, put them on the baking sheet and toss them with the remaining 1 ½ teaspoons of oil and the pepper and arrange them cut side down. Put them into the oven on the bottom shelf and roast for 12 minutes.
2 bunches of radishes, ½ teaspoon pepper
While the radishes roast, mix the butter with the miso in a small bowl.
1 tablespoon softened butter, 1 tablespoon miso
Add the greens to the baking sheet and dot the miso butter on top. Roast for 3 more minutes.
Remove the radishes from the oven and toss to mix them in the melted miso butter. Serve right away.