Andrew Scrivani for The New York Times
Meanwhile preheat the oven to 400 degrees. Line a baking sheet with parchment and brush the parchment with olive oil. Cut the sweet potatoes in half lengthwise. If they are very long, cut the halves in half crosswise as well. Cut each half into 4 long wedges – smaller sweet potatoes will yield 8 wedges, larger will yield 16.
Place the sweet potato wedges in the bowl with the oil. Add the ground cumin and coriander, and salt to taste, and toss together until the wedges are thoroughly coated with oil. Place on the baking sheet in a single layer (use 2 baking sheets if necessary). Place in the oven and set the timer for 10 minutes. Turn the wedges over and roast for another 10 minutes. Turn the wedges again and roast for another 5 to 10 minutes, depending on the thickness of the wedges and how fast they are caramelizing. The wedges should be tender when pierced and there should be some caramelized bits, especially at the thin tips. Remove from the heat and allow to cool slightly before eating.