Preheat oven to 400°F. Toast cumin seeds and coriander seeds in small skillet over medium heat until beginning to brown, about 2 minutes. Cool. Transfer to spice mill; process until finely ground. Place chickpeas, olive oil, pinch of cayenne, and ground spices in medium bowl. Sprinkle with coarse salt; toss to coat evenly. Transfer to small rimmed baking sheet. Roast in oven until lightly browned and crunchy, stirring occasionally, about 35 minutes. DO AHEAD: Can be made 4 hours ahead. Let stand at room temperature. Reheat in 400°F oven until warm, about 5 minutes, before serving.