Cover a medium-sized baking sheet with aluminum foil, and then spray with vegetable spray.
Place sweet potato cubes and onion on sheet. Coat with olive oil, salt, pepper, and garlic powder. Gently mix together and spread out to a single layer on the pan.
Roast for approximately 20-23 minutes until cooked, but “al dente” in firmness. Stir twice during cooking to prevent scorching.
Remove potato mixture from oven and cool while preparing Vinaigrette.
Place all vinaigrette ingredients except herbs in a one-pint jar with lid. Shake until combined
In a large bowl, place potatoes and onions. Pour ½ of the vinaigrette over the mixture, gently tossing. Add additional vinaigrette until potatoes are moist. Reserve any leftover vinaigrette in jar and refrigerate for up to three days.
Add herbs to potato salad, gently toss again, and serve immediately, or cover and serve at room temperature.