Combine juice, sugar and zest in a small non-reactive pan and reduce to ½ cup. Set aside.Preheat oven to 375 degrees F. Toss sweet potatoes in oil and put them into large ovenproof skillet. Do not crowd them use two skillets if necessary. Roast, tossing occasionally until lightly golden brown and just cooked through, about 35 minutes.
Remove the pan from the oven and place on a burner over medium heat.
Add the glaze to the potatoes and toss to coat evenly.