Chestnuts are highly perishable. Be sure to keep them refrigerated inside a brown paper bag. They can keep this way for up to 2 weeks.
To Roast: Soak chestnuts in water for an hour. Preheat oven to 375 F. Score the round side of each chestnut (this will prevent the chestnuts from exploding from the pressure as they roast). Arrange on a baking sheet and roast until the skins have pulled back (about 20-25 min). Peel by hand.