Broster was a member of the Wales squad that toured the USA and Canada in the summer of 2005, and was capped in games against both teams. He came off the bench to win his first cap against USA, and scored a try on his debut start against Canada.
After seven years with the London club, graduating from their academy, Broster joined the Llanelli Scarlets for one season in May 2007.
He joined Northampton Saints for the start of the 2008/09 season making one appearance in the Anglo-Welsh Cup.
In the summer of 2009 London Wasps announced the signing of the young prop on an initial one-year deal. Since joining the club he has started nearly every game and has returned to form similar to that of 2005 season. On the back of some strong performances throughout February and March Broster signed another contract keeping him at the club for a further two years.
After cementing himself as a mainstay of the Wasps team for three seasons, Broster signed a deal taking him across the channel to Top 14 side Biarritz Olympique until 2014.