Roku was the Fire Nation-born Avatar immediately succeeding Avatar Kyoshi and preceding Avatar Aang. Roku's memory served as a guiding force for Aang throughout his quest to end the Hundred Year War.

Roku was a wise and merciful Avatar with good intentions. Living in a period of change, technological revolution, and nationalist expansion, he worked tirelessly to maintain peace between the four nations during a time of complex political issues and tense diplomatic relations. However, he himself acknowledged that he was too indecisive during his lifetime. Roku's long friendship with Fire Lord Sozin resulted in his reluctance to end his friend's life and thus his imperial ambitions. This ultimately led to Roku's death, preventing him from stopping a war which would last for one hundred years, something which weighed heavily on him in his afterlife. Aang inherited Roku's burden of healing the war-torn world, and Roku firmly believed Aang was destined to amend his mistakes.