Preheat oven to 450°F. Place grapes on a rimmed baking sheet, drizzle with oil and toss to coat. Roast for 15 minutes, or until they release their juices and turn soft and squishy.
Meanwhile, heat a drizzle of oil in a medium pot set over medium-high heat and sauté the onion for about 5 minutes, until soft. Add the ginger, garlic and curry powder and cook for another minute. Add the pears, brown sugar, vinegar, chili flakes and roasted grapes, scraping any juices that have collected in the bottom of the pan into the pot, and bring to a simmer.
Cook, stirring occasionally, for about 30 minutes, until thickened. Cool completely and refrigerate for up to 2 weeks or freeze for up to 3 months.