Preheat the oven to 475°F with a rack in the middle position.
Combine the chopped sweet potatoes, salt, and oil in a large bowl tossing well to coat evenly.
Pour out onto a baking sheet with a rim lined with parchment paper.
Roast for 30-35 minutes or until fork-tender, checking once around 25 minutes to test doneness.
In a small jar with a tight-fitting lid, combine the oil, vinegar and spices. Put the top on the jar tightly, then shake vigorously.
Add more salt and pepper to suit your taste.