Start by cooking your rice. Rinse uncooked rice in a mesh strainer until water runs clear, then add to a medium saucepan with water and bring to a boil. Once boiling, reduce heat to low, cover, and cook until water is absorbed, about 20 minutes.
Meanwhile, in a small bowl or saucepan, mix together rice vinegar, sugar and salt, heat on stove or in microwave until well dissolved, set aside.
As soon as your rice is on, preheat oven to 400. Chop sweet potato into long thin strips. I aim for 1/4 inch wide strips. If they are too bulky they'll be tough to roll into the sushi. Toss in a drizzle of oil, sprinkle with a little salt, garlic and ginger, and bake until fork tender, about 15-20 minutes. Set aside to cool.
Slice tofu into small strips as well, 1/2 - 1/4 inch thick. Mix together marinade ingredients and add to tofu strips. I like to marinate in a sealed glass container that I can flip over every so often, for better distribution. Set aside.
Once your rice is cooked, stir in rice vinegar mixture until well incorporated. Allow rice to cool. If you want to help that go faster, spread rice out onto a baking sheet and refrigerate.
To assemble the sushi:
Once all your ingredients are prepared, I like to set them up assembly line style, so that everything is clearly reachable.
Place your nori on a sheet of wax or parchment paper, and use your hands to press a thin layer of rice over almost the whole sheet. Leave about an inch uncovered at the top. If it's too sticky to handle, try dipping your fingers in a bit of water. Arrange fillings on top, near bottom third of the rice.
Now, lift the wax paper and use it to help roll the nori and rice snugly around your fillings. Repeat with remaining sheets of nori.
Refrigerate whole sushi roll for at least 10 minutes, or up to 24 hours. If storing for longer than 10 minutes, place in a sealable container or wrap well in plastic or foil.
To serve, remove from fridge and unwrap. Slice with a sharp knife. Dip blade in water if you're having any issues with it being sticky!
Serve with extra soy sauce, eel sauce, wasabi, pickled ginger, or sriracha sauce.