Cook pomegranate juice, vinegar and sugar in a saucepan over medium-high heat, stirring until a thick syrup forms, 20–30 minutes. Remove saucepan from heat and reserve.
Preheat oven to 500º. Chop oregano and rosemary leaves as finely as possible. Add minced garlic and olive oil to make a paste, then smear it over all surfaces of lamb.
Season with salt and pepper, and place on a rack in a roasting pan. Brush lightly with pomegranate syrup, and place in top part of oven, bone side down, for 5 minutes.
Lower oven to 375º and roast 15 minutes per pound (or till interior reaches 125º on a meat thermometer) for medium-rare. After first 20 minutes, add some water to bottom of pan, and brush roast with more pomegranate syrup.
Allow meat to rest for 10 minutes before cutting into chops. Meanwhile, mix pan juices into remaining syrup, heat until syrup thickens, pour over chops, and serve.