Spray a large bowl with cooking spray and add the cereal. Set aside.
Line a baking tray with parchment paper and set aside.
In a large microwave-safe bowl, place the marshmallows and butter. Microwave on high for 1 minutes. Stir very well until the mixture is smooth, using the residual heat to full melt the marshmallows and butter.
Stir in the cinnamon and pour the mixture over the cereal.
Use a greased spatula to stir the mixture very well. Transfer to the baking tray.
Flatten the treats into a rough circle or rectangle about ¾-inch thick. You won't fill the entire tray. If desired, sprinkle additional cinnamon on top. Let set for 2 hours, or chill for 1 hour.
Cut out circles with the circle cutter as closely together as possible.
Prepare the frosting: In a bowl, beat together the cream cheese frosting ingredients.
Scoop the frosting into a disposable decorating bag OR ziploc bag. Snip the tip and pipe swirls on the treats. To set the frosting, return the treats to the refrigerator.