Heat the oven to 425 degrees. On a large rimmed sheet pan, drizzle the mushrooms and red onion with 3 tablespoons oil. Sprinkle with cumin, coriander, paprika (if using), 1 teaspoon salt and ½ teaspoon pepper; toss to coat. Arrange in an even layer and roast until tender and browned, about 20 minutes. Add the pitas to the oven rack to warm during the last 5 minutes of cooking.
Meanwhile, toss cabbage with remaining 2 teaspoons oil in a medium bowl; toss to coat. Season generously with salt and pepper. In a small bowl, stir together yogurt and turmeric; season with salt and pepper.
To serve, either yogurt over warm pitas. Top with cabbage, mushroom mixture and herbs, and serve immediately.
