Position rack in bottom third of oven and preheat to 400°F. Toss potatoes and oil in bowl to coat. Transfer to large baking sheet, one cut side down. Roast 15 minutes. Turn potatoes to expose other cut side. Roast until golden brown and tender, about 15 minutes. Sprinkle potatoes with 1 teaspoon chipotle powder, garlic, salt, and pepper; toss to coat. Turn potatoes skin side down. Roast 10 minutes longer.