Preheat oven to 425oF. Mix mustard with 2 tablespoon rosemary and spread over fat side of pork loin. Place in large roasting pan with 2 tablespoon olive oil. Season, roast for 25 minutes.
Meanwhile toss vegetables and pears with remaining rosemary and oil until well coated, season. After 25 minutes, reduce temperature to 325o F and add vegetables/pear mixture to pan. (You may need a second roasting pan.)
Return pan to oven and roast 70 minutes, turning vegetables ocasionally. When pork and vegetables are cooked remove to serving dish and keep warm. Add flour to roasting pan and place over medium heat. Cook stirring for 2 to 3 minutes. Gradually add pear juice and water, bring to a boil and simmer 5 minutes. Season and add vinegar. Serve with pork.
Serves 6 to 8.