In a small saucepan, combine cherries, sugar, fresh rosemary, and 1 tablespoon water. Bring to a boil over high heat. Reduce heat to medium-low, cover, and simmer until cherries are nice and tender and liquid is slightly thickened, 12 to 15 minutes.
Remove from heat and stir in vinegar; season lightly with salt and pepper. Let stand at room temperature until cool. Serve or store.