Both Richards and Roberts-Thomson were contracted until the end of next season, but have now extended their deals by a further 12 months.
Sydney Swans general manager Dean Moore told the club's website: "Both players were valuable members of the Swans premiership team, and it is exciting to have them on board for the 2013 and 2014 seasons."
Richards career was at the crossroads two years ago but he has fought back to be a key plank of the team's defence, earning All-Australian honours this year for the first time in 11 seasons.
"Ted is coming off a personal best season in 2012 that saw him named All Australian after playing on some of the game's biggest and best forwards," Moore said.
"He is an important member of our leadership group, so it is pleasing to have him re-sign."
Moore said Roberts-Thomson, who kicked a career-high 25 goals and was honoured with life membership in 2012, was an important re-signing for the club.
"There is hardly a position on the ground that LRT hasn't played in the last few seasons. He is a tremendously versatile player," Moore said
"Lewis is born and bred here in New South Wales and is a club life member so we are obviously very excited to have him extend his career at the Swans."
The Swans playing group will take a two-week Christmas break and will return to the club for pre-season training on January 7.