Preheat oven to 400 degrees.
Place yam cubes on a baking sheet and drizzle with olive oil, toss to coat then liberally sprinkle with salt and black pepper.
Spread in single layer on baking sheet.
Bake for 20 minutes, turning halfway through cooking.
Remove from oven and transfer to a plate.
Place in refrigerator to chill for about 30 minutes.
While yams are cooling, whisk together yogurt, mustard, dill, garlic, and pickle juice in a large bowl.
Fold in celery, green onions, red pepper and green olives.
Gently fold in chilled yams and return to refrigerator to chill for 30 minutes. Taste to determine if more salt and pepper needs to be added before serving.
This great salad may be prepared the day before serving with excellent results.