Prepare a workspace by laying out parchment paper and lightly coating it, your hands, and a rubber spatula with non-stick cooking spray.

In a large saucepan over low heat, melt the butter. Add the mini marshmallows and stir continuously until completely melted and smooth. Remove from heat immediately.

Gently fold the crisp rice cereal into the marshmallow mixture until evenly coated.

Turn the warm mixture onto the greased parchment paper. Press it out evenly into a large rectangle, about 1/2 inch thick.

Lay flat sheets of fruit leather over the rice cereal rectangle, leaving a small border at the top and bottom edges.

Arrange the gummy candies in a horizontal line along the bottom edge of the rectangle.

Starting from the candy edge, roll the cereal mixture tightly upwards, using the parchment paper to assist, pressing firmly to seal the seam at the end.

If the log is dry, spread a thin layer of marshmallow fluff over the outside. Roll the entire log in the Fruity Pebbles cereal until fully coated.

Wrap the log in plastic wrap and chill in the refrigerator for 15-20 minutes to firm up.

Unwrap and slice into 1-inch rounds using a greased serrated knife. Serve immediately.