1. In large plastic bowl, combine molasses, mustard and tarragon vinegar; mix well. Add pork to molasses mixture, turning to coat all sides. Marinate, covered, 1 to 2 hours at room temperature or overnight in refrigerator, turning several times.
2. Heat oven to 325°F. Remove pork from marinade; reserve marinade. Place pork in shallow roasting pan. Cook for 1 to 2 hours or until meat thermometer inserted into thickest part of roast reaches 160°F, basting with marinade* every 30 minutes; discard remaining marinade. Slice roast and garnish, if desired.