Preheat the oven to 450°F and position the racks in the top third and lower third. In a medium bowl, mix together the sweet potatoes, olive oil, cumin, coriander, and salt until the sweet potatoes are evenly coated. Spread the mixture in an even layer on two large rimmed baking sheets. Roast for 25 minutes, then gently turn the sweet potatoes and rotate the pans. Continue roasting for another 10 minutes until they are crisp and golden brown. In a small bowl, whisk together the lime zest, lime juice, crushed red pepper, and ground pepper. Pour the lime juice mixture over the sweet potatoes and toss gently to coat.