Prepare the Cauliflower Rice: If desired, heat the toasted sesame oil in a non-stick skillet over medium heat. Add the cauliflower rice and sauté for 3-5 minutes until just tender-crisp. Remove from heat and let it cool slightly. Alternatively, you can use raw cauliflower rice tossed with the sesame oil.
Set Up Your Rolling Station: Lay one nori sheet on a bamboo sushi mat, with the shiny side facing down and the longer edge parallel to you. Have your prepared cauliflower rice and sliced vegetables within easy reach.
Layer the Ingredients: Spread approximately one-third (about ½ cup) of the cooled cauliflower rice evenly over the half of the nori sheet closest to you, leaving about a 1-inch (2.5 cm) border clear along the top edge.
Add the Fillings: Arrange a selection of the red bell pepper, cucumber matchsticks, avocado slices, red cabbage, and green onion slivers in a horizontal line across the center of the cauliflower rice. Top with a handful of the chopped mixed field greens. Be mindful not to overfill, as this will make rolling more difficult.
Roll the Nori: Moisten the exposed 1-inch border of nori at the top with a little water (this helps it seal). Using the bamboo mat for support, carefully lift the edge of the nori sheet closest to you up and over the fillings. Begin to roll tightly, pressing gently but firmly with your fingers to compact the ingredients as you go. Continue rolling until you form a neat cylinder.
Rest and Repeat: Set the completed roll aside with the seam-side down to allow it to seal for a minute or two. Repeat steps 2-5 with the remaining nori sheets and fillings.
Prepare the Zesty Peanut Drizzle: In a small bowl, combine the unsweetened peanut butter, tamari, sriracha, and stevia (or your chosen sweetener). Whisk thoroughly. Gradually add the water, one teaspoon at a time, stirring continuously until the drizzle reaches a smooth, pourable consistency. Adjust seasoning and sweetness if necessary.
Slice and Serve: Using a very sharp, slightly dampened knife, carefully slice each cauli-roll into 5 or 6 bite-sized pieces. Wipe the knife clean between cuts if needed.
Present: Arrange the Rainbow Veggie Cauliflower Rice Sushi pieces on a platter or individual plates. Serve immediately with the zesty peanut drizzle on the side for dipping.