Preheat oven to 400°.
Place pita rounds on a large baking sheet coated with cooking spray, overlapping slightly. Bake at 400° for 8 minutes or until crisp, turning after 4 minutes. Let cool slightly on a wire rack.
Combine beans and chiles in a bowl; stir well. Spread about 1/3 cup bean mixture over each pita round (support the underneath side of the pita with your hand so it does not crack). Divide tomato and olives evenly among pizzas, and sprinkle with cheese. Place pizzas on baking sheet.
Bake at 400° for 8 minutes or until bean mixture is hot and cheese melts. Remove from oven; top each pizza with 1/4 cup lettuce and 1 tablespoon sour cream.