Preheat oven to 425°F (220°C).
Toss halved radishes with olive oil, garlic powder, salt, and pepper.
1 bunch radishes, 1 tsp olive oil, ½ tsp garlic powder, ⅛ tsp salt, ¼ tsp ground pepper
Spread on the prepared baking sheet, cut side down.
Roast for 25–30 minutes, flipping halfway through, until golden, tender, and caramelized at the edges. Let cool slightly.
In a medium bowl, whisk together the dressing ingredients until creamy and well combined.
2 tbsp Greek yogurt, 1 tsp Dijon mustard, 1 tsp apple cider vinegar, 1 tsp olive oil, 1 pinch garlic powder, 1 pinch salt, 1 pinch black pepper
Add the roasted radishes, chopped egg, celery, red onion, and dill to the bowl. Toss gently to coat.
1 egg, 1 stalk celery, 2 tbsp red onion, 1 tbsp dill
Taste and adjust seasoning. Chill for 15–30 minutes if time allows, or serve slightly warm.