What is black sesame?
Black sesame is a kind of slated & toasted sesame used to decorate and enrich flavor.
There isn't much to elaborate on the matter of using it, simply sprinkle as much as you dare on top, or all around an inside out sushi roll to create the desired ratio of black spots on rice white background of the roll.
The taste, by the way, is not that dominant, nevertheless sensible. Give it a try!