Sauté the cauliflower rice in a dry pan over medium heat for 3-5 minutes until tender-crisp, then stir in the rice vinegar and sea salt.
Slice the sashimi-grade ahi tuna and the cucumber into long, thin matchsticks for easy rolling.
Peel and slice the avocado into thin wedges.
In a small bowl, mix the avocado oil mayonnaise and sriracha until smooth to create a zesty spicy sauce.
Lay one nori sheet on a bamboo sushi mat and spread half of the seasoned cauliflower rice evenly across the bottom two-thirds of the sheet.
Place half of the tuna, cucumber, and avocado in a horizontal line across the center of the rice.
Carefully roll the nori from the bottom up, using the mat to keep it tight, and seal the top edge with a small amount of water.
Repeat the process for the second roll, then slice each into eight rounds with a sharp, wet knife and garnish with sesame seeds and coconut aminos.