Place raspberries in a bowl; sprinkle with sugar and mash. Let stand for 15 minutes; mash again. Strain, reserving juice; discard pulp and seeds.
In a small saucepan, combine the raspberry juice, apple juice, vinegar, garlic and 1/4 teaspoon sage. Simmer, uncovered, for 5 minutes. In a small bowl, combine cornstarch and water until smooth; stir into raspberry juice mixture until smooth. Bring to a boil; cook and stir for 1 minute or until thickened.
Combine the salt, pepper and remaining sage; rub over roast. Place fat side up on a rack in a shallow roasting pan. Spread with 1/2 cup raspberry sauce.
Bake, uncovered, at 350° for 1-3/4 to 2 hours or until a thermometer reads 160°. Let stand for 10-15 minutes before slicing. Meanwhile, reheat the remaining raspberry sauce; serve with pork.