Heat oven to 425°F. Using a heavy pan, coarsely crush coriander seeds.
Peel potatoes, halve lengthwise, then cut into ½-inch-thick pieces.
Transfer to a rimmed baking sheet and toss with oil, coriander, cinnamon, ½ teaspoon salt, and ¼ teaspoon pepper.
Roast, turning once halfway through, until tender, 40 to 50 minutes. Transfer to a serving platter.
In a small bowl, whisk together yogurt and lemon juice until smooth. Drizzle over potatoes and sprinkle with chili and feta.
