1.Preheat oven to 200°C/400°F.
2.Combine tomatoes, cheese and spinach in medium bowl.
3.Cut a horizontal pocket in each roast; do not cut all the way through. Press half the mixture into each pocket; secure with toothpicks.
4.Heat oiled small baking dish over high heat. Cook lamb, turning, until browned all over. Transfer dish to oven; roast lamb, uncovered, about 20 minutes or until cooked as desired.
5.Cover; stand for 10 minutes before serving.