Rinse rice well. Combine rice and water in saucepan, cover, bring to boil, lower heat to simmer, and cook without stirring until water is gone, about 15 minutes.
Meanwhile, prepare the vegetables and cut into strips.
Put rice in the larger bowl and stir in vinegar.
Lay out a sheet of nori on the sushi mat, if you have one, or on the counter. Spread a 2-inch wide strip of rice all the way across the bottom end of the nori, leaving ½ inch at the bottom. The rice layer should be thick enough that you can’t see the nori underneath it.
Place strips of vegetables on top of the rice, so that there is a line of each all the way across.
Beginning at the bottom, roll up the nori fairly tightly, but be careful not to tear it. When you get near the top, dab a stripe of soy sauce along the edge and finish rolling to seal the maki roll.
Once you’ve rolled all four, slice them into 6 to 8 bite-sized wheels.
In the small bowl, mix wasabi powder with a few drops of water to make a thick paste. You can serve it this way, or add soy sauce to taste.
Serve the maki rolls with the wasabi or wasabi/soy sauce as well as a dish of plain soy sauce for those who don’t like spicy stuff.