To season the rice: In a small bowl, whisk together the rice vinegar, sugar, and salt. Pour the mixture over the warm steamed rice and gently fold until evenly coated. Set aside.
To make the tuna filling: In a medium bowl, combine the drained tuna, Japanese mayonnaise, and sriracha until well mixed.
To prepare the avocado: Squeeze the lemon juice over the avocado slices to help prevent browning.
To prepare the rice paper: In a shallow bowl, whisk together the water and rice vinegar. Lightly brush both sides of each rice paper sheet until just softened.
To assemble the sushi rolls: Place a roasted seaweed sheet in the center of a softened rice paper sheet. Spread about 2 tablespoons of seasoned rice over the seaweed and sprinkle with the toasted sesame seeds. Add the tuna filling, shredded carrots, avocado slices, and tobiko. Fold in the sides and roll tightly like a burrito. Repeat with the remaining ingredients.
To pan-fry the sushi rolls: Heat the avocado oil in a large pan over medium heat and sprinkle in a pinch of salt. Place the rolls seam-side down and pan-fry for about 4 minutes, turning until all sides are golden and crispy. Repeat with the remaining rolls.
To make the dipping sauce: Stir together the soy sauce and wasabi until well combined.
To serve: Slice the rolls in half if desired and serve immediately with the dipping sauce.