In a large microwave-safe bowl, add marshmallows and butter. Microwave for 1-2 minutes until puffy and melted. Remove and stir well with a rubber spatula.
Add Rice Krispies cereal and mix until coated with marshmallow. Set aside to cool. In a small microwave-safe bowl, heat chocolate candy pieces for 3-4 minutes at 50% power, stirring every 30 seconds until melted.
Don't overheat the chocolate, or it will become a hard ball. Hold each ice cream cone upside down and dip into the melted chocolate. Shake off any excess chocolate.
Immediately coat the chocolate with 4th of July sprinkles and freeze for about 15 minutes. Scoop a handful of Rice Krispies, form a ball, and press into the cone to resemble a scoop of ice cream.
Sprinkle most of the 4th of July Sprinkles onto the top of the Rice Krispies. Press them down if you need to.