Add the chopped cauliflower florets to a food processor and pulse until the texture resembles rice.
Transfer the riced cauliflower to a microwave-safe bowl, sprinkle with the salt, and microwave on high for 4–5 minutes until tender.
Wrap the cooked cauliflower in a clean towel or paper towels and squeeze or press to remove as much moisture as possible, then let it cool completely.
When cool, stir in the white vinegar and sugar-free powdered sweetener until evenly combined; this is your cauliflower "sushi rice."
Place a nori sheet on a flat surface and divide half of the cauliflower rice across the sheet, leaving about 1/4 inch (6 mm) border around the edges.
Spread 1 tablespoon mayonnaise over the rice, arrange half of the salmon (or chosen protein) and half of the cucumber strips along the center, and sprinkle with sesame seeds; add a thin line of wasabi if using.
Roll the nori tightly around the filling, removing any filling that escapes, then repeat the process with the second nori sheet and remaining ingredients.
Using a sharp knife dipped in water, slice each roll into pieces and serve.