Place the cooked sushi rice in a small bowl and gently fold in the rice vinegar until well combined and slightly sticky.
Slice the sushi-grade ahi tuna and salmon into long, thin strips approximately half an inch thick.
Peel and julienne the cucumber into thin matchsticks and slice the avocado into long slivers.
Place one nori sheet on a bamboo rolling mat with the rough side facing up.
Spread half of the seasoned rice evenly over the bottom two-thirds of the nori sheet, leaving the top edge clear.
Layer half of the tuna, salmon, cucumber, and avocado horizontally across the center of the rice.
Lift the edge of the bamboo mat and roll the nori tightly over the filling, using a drop of water to dampen and seal the top edge.
Repeat the process with the second nori sheet and the remaining ingredients.
Use a very sharp, damp knife to slice each roll into six to eight even pieces.
Serve the rolls immediately with coconut aminos, wasabi paste, and pickled ginger on the side.