Butterfly loin lengthwise; gently pound with meat mallet to a thickness of 1/4-inch.
Combine sausage, apples, chopped yellow onion, carrots, turnip, 1 tablespoon rosemary, and pepper well; spread the sausage mixture evenly over loin.
Roll up loin; tie with butcher twine every 1/2-inch.
Brown roast in a large skillet and then remove to shallow roasting pan and roast for 45 minutes - one hour, until internal temperature (measured by a meat thermometer) reads 155 degrees F. Let pork rest for 10 minutes before removing twine and slicing to serve.
Rosemary Currant Sauce: Soak currants in orange juice; set aside. In saucepan, simmer wine and minced onion; reduce to 1/2 cup and add currant jelly. Add beef broth and simmer to reduce again by half.
Dissolve cornstarch in water, stir into sauce and bring to a boil. Cook, stirring constantly, until slightly thickened. Stir in orange juice and currants and one tablespoon minced rosemary. serve with sliced roast.