Line a 10x15-inch jelly-roll pan with parchment paper and lightly butter the parchment; set the pan aside.

In a large microwave-safe bowl, combine 10 oz miniature marshmallows and 1/4 cup butter. Cover and microwave on high for 30 seconds, stir, then repeat 30-second intervals, stirring between each, until the marshmallows and butter are completely melted and smooth.

Add 6 cups Cocoa Krispies cereal to the melted marshmallow mixture and stir until the cereal is evenly coated.

Press the cereal mixture firmly and evenly into the prepared pan.

In a separate microwave-safe bowl, combine 7 oz marshmallow creme and 1/2 cup creamy peanut butter. Microwave for 30 seconds, then stir; if needed, microwave an additional 10–15 seconds and stir until the mixture is smooth and spreadable.

Spread the marshmallow-peanut butter mixture evenly over the pressed Rice Krispies layer.

Evenly sprinkle 2 cups roughly chopped Reese’s peanut butter cups over the top and press down lightly to adhere.

Starting at the long side of the pan, use the parchment to roll the layered slab into a tight jelly-roll, peeling the parchment away as you roll; pinch the seam to seal.

Place the roll seam-side down on the pan and refrigerate 30–45 minutes, or until the peanut butter cups’ chocolate has set and the roll is firm.

Remove from the refrigerator, slice into pinwheels with a sharp knife (wipe the knife between cuts for cleaner slices), and serve.