Rinse quinoa thoroughly. Bring quinoa and water to a boil. Reduce to a simmer and cook until water is absorbed, about 15 minutes.
Heat brown rice vinegar, sugar, and tamari in a pan until the sugar dissolves. Pour over cooked quinoa. Mix thoroughly.
Cut sweet potato into large chunks. Put sweet potato and enough water to cover them in a pot. Bring to a boil, then reduce to a simmer. Cook until tender. Let cool.
Lay a nori sheet out on a cutting board with the perforated lines going vertically (if your nori has perforated lines). Spread ½ cup cooked quinoa on nori sheet, pressing quinoa into nori and leaving about ½" of the far side uncovered.
Slice sweet potato into strips. Layer sweet potato strips on quinoa along with 2 red pepper strips. 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.
Miso Ginger Dipping Sauce: Mix all the ingredients.