Preheat oven to 180°C. Place Lamb in a baking tray. Combine olive oil and garlic and brush over Lamb.
Toss potatoes in extra oil and rosemary and place around the Lamb. Roast for 1 hour, basting Lamb occasionally with garlic oil. Add tomatoes for last 20 minutes of cooking.
Cover and rest Lamb for 15 minutes before carving.
Pour pan juice into small saucepan. Combine cornflour with 2 tbsp water and stir until smooth. Add to pan juices along with beef stock. Bring to the boil, reduce heat and stir until thickened. Serve alongside Lamb.
Notes & Tips
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