William Royce was a US senator. He was Aaron Marker's boss. Also runs and becomes President of the United States
Royce was present at a CIA briefing on Operation Troy. When Aaron told the CIA about Operation Troy, Royce told Aaron he was in a lot of trouble.
He helped Cassandra Railly visit Chechnya to confirm Cole had been erased from the timeline.
When Royce announced his campaign for president, he fired Aaron because the latter's connections to the Operation Troy controversy were too much baggage. When Aaron met with him to discuss Aaron's future, he agreed that Aaron would be well-suited to work on a project for sheltering selected survivors in case of a disaster.
William Royce is elected President
It is believed (Season 4 Episode 2) that Royce is not immune but information is unknown if he suffers the Kalavirus and dies from it later or is violently overthrown.