Roger Benoit was the French assistant to Jack Hobson on the Moonbase. He was a physicist and second in command to Hobson.
He was doing checks on the Gravitron controls when the Second Doctor, trying to find the cause of the infection on the Moonbase and collecting samples for experimentation, cut a piece from his trousers. Benoit realised what the Doctor was doing and yelled at the Doctor in French.
When Jules and Franz failed to report back from the surface, Benoit went outside the Moonbase to check on them. While out there, he was attacked by a Cyberman. He made it back to the base, with the Cybermen chasing him. He was saved when Ben sprayed the Cybermen with Polly's plastic-dissolving compound.
When the Cybermen shot a hole in the Moonbase, he and Hobson quickly covered the hole to keep the oxygen from rushing out. He then worked the controls of the Gravitron to aim it at the Cybermen, sending them floating away from the moon. (TV: The Moonbase)
Behind the scenes
Benoit's first name was originally Jules, but in rehearsals it was discovered that one of the other scientists was also named Jules, so Benoit's first name was changed to Roger. However, the name tags for the scientists had already been made, so the tag still said "Benoit J". It was then decided to gives Benoit a neck tie to cover up most of the name tag. (INFO: The Moonbase) In the novelisation, his first name is reverted to Jules.