Position racks in top third and lower third of oven; preheat to 450°F. Stir sweet potatoes, oil, cumin, coriander and salt together in a medium bowl until the sweet potatoes are evenly coated. Spread in an even layer on 2 large rimmed baking sheets.
Roast for 25 minutes. Turn the sweet potatoes gently and rotate the pans; continue roasting until crisp and golden brown, about 10 more minutes.
Meanwhile, whisk lime zest, lime juice, crushed red pepper and pepper together in a small bowl until combined. Pour the lime juice mixture over the sweet potatoes; gently toss to coat.
