Toss pita, Halloumi, and remaining 1 Tbsp. oil in reserved bowl. Scatter over vegetables, then turn vegetables over with a large spatula. Roast until squash is fork-tender and cabbage, onion, pita, and Halloumi are browned in spots (cheese should be soft inside), 15–20 minutes. Remove from oven and drizzle with vinegar. Top with sumac and mint.
Photo by Laura Murray, food styling by Mariana Velasquez