In a large bowl toss the grapes with olive oil, salt, pepper and chile pepper to combine.
Arrange grape mixture in a single layer on a baking sheet.
Transfer baking sheet to oven and roast, shaking pan intermittently, until grapes have burst and grape juice begins to thicken, about 20-25 minutes. Let cool and transfer to serving dish.
Roasted grapes will keep in the refrigerator for up to 5 days.