Preheat the oven to 425 degrees F. Spray a heavy baking sheet with vegetable oil cooking spray.
In a medium bowl, toss together the red onion, red pepper, zucchini, garbanzo beans, oil, cumin, Italian seasoning and salt.
Spread the mixture in a single layer on the baking sheet. Roast until the vegetables are golden and tender, 25 to 30 minutes. Toss mixture after 15 minutes of cooking time.
During the last 10 minutes of vegetable cooking time, place the pitas in the oven on the unused rack until warm, about 4-5 minutes.
On each pita spread a layer of hummus, ¼ of the vegetable and bean mixture, sprinkle with feta and black olive slices. Drizzle with spicy yogurt sauce.
Spicy Yogurt Sauce
In a small bowl, mix together the yogurt, lime juice, agave and chipotle pepper until smooth.