If you don't have leftover sweet potatoes, bring water to boil in a large pot, and boil sweet potatoes for 40-50 minutes. You can also wrap the potatoes in aluminum foil and bake at 400° F for 50 minutes.
While the potatoes are boiling or baking, cook the sushi rice according to package in rice cooker.
While potatoes and rice are cooling, make the spicy mayo sauce.
Lay the nori sheet on a clean workplace, and spread a thin layer of rice over the sheet. Leave one inch bare at the furthest side from you to seal the roll later.
Layer the sweet potato and spicy mayo on the closest side to you. Roll up the roll and use a little water to seal the edge.
Wet a knife and gently slice your roll. Top with extra sauces of your choosing.