Preheat oven to 425°F and line a baking sheet with parchment paper.
Toss the veggies with the olive oil, garlic powder and salt. Place on the baking sheet. Roast for 25-30 minutes or until slightly golden.
While the radishes and potatoes are roasting, make the dressing. Add all ingredients for the dressing to a blender or food processor and process until smooth.
Serve the potatoes and radishes on a bed of microgreens (if desired) and top with kefir dressing.