Preheat oven to 400°F. Sprinkle each pear half with brown sugar and rosemary, dividing evenly. Arrange pears in glass pie plate. Bake until tender and golden, about 20 to 30 minutes. Sprinkle half of cheese over each. Bake until cheese melts, approximately 5 minutes. Place pears on plates. Spoon 1 tablespoon of Port over each and serve.