Cut the radishes in half. Toss in 2 tablespoons olive oil and salt until well coated. Spread radishes evenly in a baking dish or sheet pan and roast for 15-25 minutes until tender, tossing every 5 minutes.
In a blender, add the feta cheese, greek yogurt, garlic powder, onion powder lemon zest, and lemon juice. Blend while slowly incorporating the remaining olive oil until well incorporated.
Spread whipped feta on a serving plate, top with roasted radishes, parsley, and black pepper.