Defrost the fish until it will spread evenly and divide into five equal portions.

Preheat the oven to 350 degrees Fahrenheit. Place a sheet of nori seaweed, shiny side down, on a flat surface. Gently spread one portion of gefilte fish on the seaweed. Arrange the sliced red peppers in a single row along one edge of the sheet. Follow with a row of shredded carrots alongside the peppers. Starting from the side with the peppers and carrots, tightly roll up the nori sheet jelly-roll style.

Repeat with the four remaining nori sheets. Transfer the rolls to a baking pan and bake, uncovered, for 25 minutes. Allow to cool, then refrigerate until firm.

When ready to serve, slice the rolls into one-inch pieces. Serve cold, with your choice of horseradish, soy sauce, wasabi sauce, or mayo for dipping.