Wash the beets and slice the tops and ends off.
Bring a large pot of water to a boil over medium heat and cook the beets until fork-tender, 30-45 minutes. Drain and allow to become cool enough to handle.
Preheat the oven to 375 degrees F. Line a baking tray with parchment paper.
Peel the beets and cut them into wedges. Place them on the prepared baking tray and drizzle with 2 Tbsp of the oil and 1/4 C of the balsamic. Toss well to ensure the beets are well-coated. Sprinkle with salt and pepper to taste and roast in the oven for 15-18 minutes, until the beets are caramelized and the edges start to crisp.
In a small frying pan over medium heat, place the walnuts and dry-toast them until they are just browning around 3-4 minutes. Remove from heat and set aside.
While the beets are roasting, whisk together the remaining 2 tbsp of oil, 1 Tbsp of balsamic and yogurt. Add salt and pepper to taste. Remove beets from oven and allow to cool slightly.
Transfer the beets to a large mixing bowl and top with the yogurt dressing. The yogurt will turn a lovely pink color. Divide salad between serving plates and top each one with the walnuts.