In a 13x9 baking dish add the bottom half of your bread rolls. Drizzle with melted peanut butter. Top with the chocolate bars and mini marshmallows. Add the top of your rolls. Brush with remaining melted butter. Top with crushed graham cracker pieces. Bake for 10-12 minutes or until chocolate has melted and marshmallows have puffed up a bit. Eat warm!