Preheat your oven to 200°C (390°F). Gather a baking dish or rimmed sheet and set it nearby.
Wash the radishes thoroughly and pat them dry. Place them in a mixing bowl, then drizzle with olive oil and toss until evenly coated. Tuck in the whole garlic cloves with skins on.
Arrange the radishes cut side down on the baking sheet, spreading them out evenly. Nestle the garlic cloves among the radishes. Sprinkle generously with coarse sea salt and cracked black pepper. Add fresh herbs if using.
Slide the baking sheet into the oven and roast for about 25-30 minutes. Check after 15 minutes, and give the pan a gentle shake or flip the radishes to promote even caramelization.
Look for golden-brown caramelized edges on the radishes and soft, fragrant garlic cloves. The radishes should feel tender when pierced with a fork and smell sweet and smoky.
Remove the baking sheet from the oven and let the radishes rest for 5 minutes. Squeeze fresh lemon juice over the roasted vegetables, then toss gently to combine.
Transfer the roasted radishes and garlic to a serving dish. Drizzle with additional olive oil if desired, and sprinkle with extra herbs or seasoning for a finishing touch. Serve warm or at room temperature, enjoying the tender, caramelized edges and fragrant aroma.