Place the pork, fat-side-up, in large heavy roasting pan. Insert a meat thermometer in the center of the roast. Roast for 30 minutes.
In a small bowl, stir the rosemary with the olive oil, pepper, vinegar and salt. Spoon over the pork and spread all over.
Return the pork to the oven and roast about 30 minutes longer or until the internal temperature is 140 to 145℉. Remove from the oven, cover loosely with foil, and let rest for at least 10 minutes.
Slice thinly and pour any juices over the meat. Serve warm or at room temperature.