Add all ingredients to a large mixing bowl; toss until well combined. Pour mixture evenly onto a rimmed baking sheet; roast in a preheated 450° oven for 10 min. Watching carefully to make sure juices don’t burn, continue roasting grapes, stirring occasionally, until liquid has thickened and grapes have mostly burst (6-8 min.). Remove from oven and cool to room temperature. Serve immediately or store, covered, in the refrigerator for up to 3 days.