Strip the leaves off 2 rosemary sprigs. Finely chop the leaves of 1 sprig. Set aside the remainder of the bunch of rosemary.
Using the tip of a sharp, slender knife, make a series of ½-inch-deep holes in the lamb, mostly in the sheath of fat on top, but also on the sides and bottom. The holes should be about 1 inch apart. Insert the garlic, olives, and whole ro