Ross, who will continue to be registered as a player, will work alongside newly appointed head coach Justin Burnell.
Ross, 35, has amassed 574 points in 106 appearances for the Exiles since joining the club in 2009 from Saracens. He won the first of his 25 caps for Scotland in 2001 against Tonga, scoring a debut record 23 points, and went on the summer tour to North America. Ross began his playing career with Heriot’s FP before joining Edinburgh in 2000. His former clubs also include Leeds Carnegie and Castres.
He said: “It was disappointing last year to get relegated, but this is a new challenge. I will still be registered as a player. I still love playing and, if I’m called upon, I will, as always, give my all for London Welsh.”