Quinoa: Rinse quinoa thoroughly. Bring water and quinoa to a boil, then reduce to a simmer. Add salt. Cook for about 15 minutes. Let sit for 5 minutes until the water is absorbed and quinoa is fluffy and tender.
Sushi Rolls: Lay a nori sheet out on a cutting board with the perforated lines going vertically (if your nori has perforated lines). Spread ½ cup quinoa on nori sheet, pressing quinoa into nori and leaving about ½" of the far side uncovered.
Layer 2 tofu strips and 2 cucumber slices on quinoa. Top with chopped green onion. Roll tightly away from you. Wet the uncovered edge so that the roll will stick. Slice on perforated lines with a serrated knife, or to the size of your liking. Repeat with the other rolls.