Preheat oven to 425° F. Arrange pork in a large roasting pan and season, if desired, with salt and pepper. Roast for 1 hour.
Meanwhile, bring water and next 4 ingredients to a boil in a medium saucepan, stirring to dissolve bouillon. Boil about 3 minutes or until sauce is reduced slightly. Stir in jelly and continue to boil an additional 3 minutes or until sauce is slightly thickened, stirring occasionally. Reserve 1 cup. Brush remaining glaze over pork and continue to roast until a meat thermometer inserted in roast reaches 160°F. Serve sliced pork with reserved guava sauce.