Preparation Preheat oven to 350°F. Using on/off turns, blend olives, garlic and rosemary in processor until chopped. Gradually add oil, blending until coarse paste forms. Season paste with salt and pepper. Sprinkle lamb with salt and pepper. Place lamb, boned side up, on rimmed baking sheet. Spread olive paste over top of lamb. Roast lamb 30 minutes. Increase oven temperature to 400°F. Continue roasting until thermometer inserted into thickest part of lamb registers 135°F for medium-rare, about 20 minutes. Let stand 15 minutes.
Preparation Preheat oven to 350°F. Using on/off turns, blend olives, garlic and rosemary in processor until chopped. Gradually add oil, blending until coarse paste forms. Season paste with salt and pepper. Sprinkle lamb with salt and pepper. Place lamb, boned side up, on rimmed baking sheet. Spread olive paste over top of lamb. Roast lamb 30 minutes. Increase oven temperature to 400°F. Continue roasting until thermometer inserted into thickest part of lamb registers 135°F for medium-rare, about 20 minutes. Let stand 15 minutes.