Lightly sauté cauliflower rice in a dry pan for 3–4 minutes until just tender; don’t overcook.
Stir in rice vinegar, sesame oil, sweetener, and salt. Let cool completely.
Place a nori sheet shiny side down on a bamboo mat. Spread cauliflower rice evenly, leaving 1 inch uncovered at the top.
Arrange fillings (fish, avocado, cucumber, etc.) in a line across the center.
Roll tightly using the mat, sealing the edge with a little water.
Slice into 6 pieces with a sharp knife. Repeat with remaining ingredients.
Serve with soy sauce, wasabi, and pickled ginger.