In a 5- to 6-quart pan over high heat, bring about 3 quarts water to a boil. Add noodles and cook until tender to bite, 3 to 6 minutes. Drain noodles and rinse gently under cold running water until cool.
Meanwhile, in a large bowl, mix rice vinegar, sesame oil. soy sauce, ginger, and wasabi, if using. Pour about half the dressing into a small container; cover and reserve. Add noodles to large bowl and mix to coat; cover and chill until cold, about 1 hour, or up to 1 day.
Just before serving, add protein, vegetables, and reserved dressing to noodles; mix to coat.