Clear off a good work surface and lay out the sheets of nori.
Have a small bowl of water nearby to dip your finger in for "gluing" the ends of the nori to the roll.
Place 1 slice of cucumber, 1 slice of avocado and small bit of tuna towards one end of the nori.
Moisten the other end with some water, and roll everything up like a carpet, pressing the wet end into the dry part a bit to get it to stick well. Use liberal finger dips of water to get the nori to stick well.
To make the sauce, simply whisk the two sauce ingredients together in a bowl and serve as a dipping sauce with the sushi rolls.