Preheat oven to 425.Cut the top tip of the head garlic off, just enough to expose all of the cloves. Place garlic on a separate piece of tin foil. Drizzle with olive oil and seal the foil around the garlic.Place garlic packet on a baking sheet or baking dish. Roast in the oven for 30 minutes. Remove from oven and allow to cool.In a food processor, add the cream cheese, cornstarch, sour cream, white cheddar and Sriracha. Squeeze the head of garlic until the cloves come out, add the soft cloves to the food processor, discard the rest of the head.Process until smooth.Add dip to a saucepan over medium high heat. Cook, stirring frequently, until bubbling. Transfer to a serving dish.