1. Place the cooked sushi rice in a small bowl and gently fold in the rice vinegar until well combined.
2. Slice the sushi-grade salmon and cooked wild-caught shrimp into long, thin strips approximately 0.5 inches thick.
3. Slice the cucumber into thin matchsticks and the avocado into slim wedges.
4. Place one nori sheet on a bamboo rolling mat and spread half of the rice evenly over the bottom two-thirds of the sheet.
5. Generously layer half of the salmon, shrimp, cucumber, and avocado in a horizontal line across the center of the rice.
6. Carefully lift the edge of the mat and roll the nori over the filling, pressing firmly to create a tight cylinder.
7. Repeat the process with the second nori sheet and the remaining ingredients.
8. Using a very sharp, slightly damp knife, slice each roll into 6 to 8 bite-sized pieces.
9. Serve the fresh rolls immediately with wasabi paste, pickled ginger, and tamari for dipping.