Season the lamb shanks with the salt and pepper. Place a roasting pan large enough to hold the shanks in one layer in the oven and heat for 5 minutes. Add the shanks to the pan and brown (no oil is needed, as shanks have enough exterior fat), turning a few times to brown all sides, about 20 minutes. Remove the shanks from the pan and set aside. Pour off all but 2 tablespoons of the rendered fat. Add the garlic and rosemary to pan, stir, and continue to cook for 2 minutes more, being careful not to burn the garlic. Add the wine and cook to reduce by one-third, about 6 minutes. Return the shanks to the pan and add 2 cups stock to cover no more than one-third the level of the meat. Cover the pan tightly with foil and roast, checking periodically, turning the shanks and adding more stock if necessary, about 3–3 1⁄2 hours. Remove from oven, squeeze the juice from the lemon over the shanks, add the zest and parsley to the pan juices, and serve.