In a large saucepan, combine the Traminette wine, honey, water and sugar and bring to a boil.
Boil until reduced by half, about 30 minutes.
Add the rosemary sprig and let stand for 10 minutes; discard the rosemary.
Preheat the oven to 350°.
Arrange the peaches in an 8-by-11-inch baking dish.
Pour the rosemary syrup on top and roast the peaches until tender, 40 minutes, basting and turning the peaches occasionally.
Serve with vanilla ice cream.