1.Preheat oven to 220°C.
2.In a medium shallow baking dish, combine kumara, garlic, rosemary, chilli and oil. Roast about 20 minutes or until kumara is tender.
3.Meanwhile, in a medium frying pan, melt butter; cook onion, stirring occasionally, about 15 minutes or until caramelised.
4.Place pita on oven trays; spread with pasta sauce. Divide kumara and onion among pita; sprinkle with cheese.
5.Bake pizzas about 10 minutes or until pita bases are crisp and topping is heated through. Just before serving, sprinkle with mint.