1.Combine yoghurt, juice, garlic, oregano and cumin in a large bowl, remove half and reserve. Add lamb to remaining yoghurt, toss to coat. Thread lamb onto four wooden skewers. Stir cucumber and mint into reserved yoghurt mixture.
2.Drizzle lamb skewers with oil. Cook over high heat in an oiled grill pan (or on a grill or barbecue) until cooked as desired.
3.Warm pita in microwave on HIGH (100%), 20 seconds. Divide rocket, tomato and onion among pita, top with lamb skewers and drizzle with reserved yoghurt mixture.
4.Roll pita tightly to enclose filling. Holding pita tightly, pull skewer from meat and discard. Serve immediately.