Place pears in a large pot with water, sugar, wine, cinnamon sticks, lemon juice, and rosemary. Bring to a simmer and cook until a paring knife slides easily into them (about 30 minutes). Transfer pears to a large plastic container; refrigerate, allowing them to cool in their poaching liquid.
To make the syrup, place port in a medium saucepan and simmer over medium-high heat until it just begins to get syrupy, about 15 minutes (it will thicken as it cools).
Remove the cooled pears from liquid and stuff the cores with equal amounts of blue cheese. Roll the filled pears in chopped pistachio nuts (you might find it easier to sprinkle the nuts on a piece of aluminum foil, then wrap the foil around the pear, pressing them in). Stand each pear in the center of a plate and drizzle syrup around it. Garnish with triangles of blue cheese.