Make sure to carefully follow each step of the instructions for the best results :
- Preheat the oven.
Set the oven to 425°F and line a large sheet pan with parchment paper. A hot oven is key to getting caramelized, slightly crispy edges on the radishes, which is what brings out their best flavor and texture. - Prep and trim the radishes.
Wash the radishes well, trim the stems and root tips, and cut them in half. If any radishes are very large, quarter them so all the pieces are roughly the same size and cook evenly. Cutting them flat-side down also helps them develop a golden surface during roasting. - Toss with oil and seasoning.
In a large bowl or directly on the sheet pan, toss the radishes with olive oil or melted butter, salt, black pepper, onion powder, and red pepper flakes if using. Spread them in a single layer with the flat cut side facing down. Using butter instead of olive oil gives a richer, more potato-like flavor that many low carb versions specifically recommend. - Roast until caramelized.
Roast the radishes for 15 minutes, then remove the pan and add the minced garlic and fresh thyme or rosemary. Toss to coat, then return to the oven for another 10 minutes until the radishes are tender, golden, and slightly caramelized at the edges. Adding the garlic halfway through roasting prevents it from burning while still giving it enough time to flavor the radishes. - Finish and serve.
Remove from the oven and drizzle with lemon juice. Scatter the fresh parsley, chives, or dill over the top and finish with a pinch of flaky sea salt if desired. Fresh herbs added after roasting keep the color and flavor bright and vibrant.