Preheat the oven to 425 degrees F. Toss the sweet potatoes on a large, foil-lined rimmed baking sheet with the oil; season, to taste, with salt and pepper. Roast the potatoes for 20 minutes.
Remove the pan from the oven and toss the potatoes with the syrup.
Back in the oven, roast, tossing twice, until the potatoes are beginning to brown and are tender, about 15 minutes more. To serve, sprinkle warm potatoes with freshly grated lemon zest, sea salt, and nutmeg to taste.
