Step 1

Heat oven to 400°F.

Step 2

Pierce lamb in several places with sharp knife. Stuff rosemary and 8 garlic cloves into slits in lamb; place in large roasting pan.

Step 3

Combine vegetables and remaining garlic in large bowl. Whisk dressing, mustard and oil until blended. Pour half the dressing mixture over vegetables; toss to evenly coat. Brush remaining dressing mixture onto lamb; sprinkle with pepper.

Step 4

Remove potatoes from vegetable mixture; place, cut sides down, around lamb in roasting pan. Spread remaining vegetables onto rimmed baking sheet sprayed cooking spray.

Step 5

Bake lamb and potatoes 50 min., reducing oven temperature to 350°F after 30 min. Add pan of vegetables to oven. Bake 40 min. or until lamb is done (160ºF) and vegetables are tender.