In a medium saucepan, melt 4 cups of marshmallows along with 2 tablespoons of butter over low heat, stirring continuously for about 5–7 minutes until completely smooth and gooey.

Once the marshmallow mix is smooth, quickly stir in 6 cups of Fruity Pebbles cereal until all the pieces are fully coated. This should take about 1–2 minutes.

Grease your hands with a little butter or non-stick cooking spray to prevent sticking. Scoop the marshmallow-cereal mixture onto a large piece of parchment paper and press it into a rectangular shape about 1/2 inch thick.

Sprinkle your choice of optional fillings onto the center of the flattened mixture, leaving about an inch around the edges.

Using the parchment paper as a guide, carefully lift one edge and start rolling the sushi mixture tightly away from you. Gently press as you roll to ensure it holds together.

Let your roll sit for about 10 minutes to firm up before slicing into bite-sized pieces about 1-inch thick.