Combine salt and pepper; rub over pork. Place in a 13x9" baking pan coated with nonstick cooking spray. Place one sprig of rosemary under the pork and one on top. Bake, uncovered at 425 for 10 minutes.
Meanwhile in a saucepan, heat preserves and horseradish until preserves are melted; stir until blended. Remove top rosemary sprig. Brush pork with 1/4 c. pineapple sauce. Bake 10-20 minutes longer until meat thermometer reads 160. Let stand for 5 minutes before slicing. Serve with remaining sauce.