Roasted Radishes and Onions

Bahan-bahan (6 porsi)

• 2 large bunches radishes (about 1 pound each trimmed of the greens)
• 1 pound spring onions or shallots
• 1 tablespoon extra virgin olive oil
• ½ teaspoon kosher salt (plus more to taste)
• ½ teaspoon coarsely ground black pepper