Roby made his début in 2004 against Widnes after progressing through the academy ranks at St Helens. Roby's position is usually as a hooker and has plenty of experience already, playing alongside some of the greats of the game including Keiron Cunningham. Roby has made a massive impact for St. Helens and has played over 50 games for them. In 2005's Super League X, he was narrowly beaten to the Young Player of The Year. St Helens see James as one of the brighter prospects and he seems a perfect replacement for Keiron Cunningham when he retires, so much so that St. Helens were willing to allow Mickey Higham to leave the club and Roby was given a more active role in the team. Roby played for St Helens from the interchange bench in their 2006 Challenge Cup Final victory against Huddersfield. St Helens reached the 2006 Super League Grand final to be contested against Hull FC, and Roby played from the interchange bench in Saints' 26–4 victory. As 2006 Super League champions, St Helens faced 2006 NRL Premiers the Brisbane Broncos in the 2007 World Club Challenge. Roby played at in the Saints' 18–14 victory. Roby holds the honour of scoring the first try at the new Wembley Stadium, scored during St Helens' victory over Catalans Dragons in the Challenge Cup Final on 25 August 2007. Roby also won the 'Man of Steel' award in October 2007 after being judged to have had the most impact on 2008's Super League XIII season, being the youngest player to ever win the award, and also becoming the third St Helens player in a row to win the accolade from 2005 to 2007, with Jamie Lyon and Paul Wellens winning the award previously. He played in the 2008's Super League XIII Grand Final defeat by Leeds. He played in the 2009 Super League Grand Final defeat by the Leeds Rhinos at Old Trafford.
2010s
He played in the 2011 Super League Grand Final defeat by the Leeds Rhinos at Old Trafford. Despite being linked with moves to the NRL, Roby committed his long-term future to St Helens in 2013 by signing a 5-year contract with the club. St. Helens reached the 2014 Super League Grand Final, and Roby was selected to play at hooker, putting in a Man-of-the-Match performance to claim the Harry Sunderland Trophy in their 14–6 victory over the Wigan Warriors at Old Trafford.
2018
On 23 January 2018 Roby was appointed captain for 2018 The 32-year-old takes over the role from back rower Jon Wilkin.
Roby was selected for the England squad to compete in the 2008 World Cup in Australia. Group A's first match against Papua New Guinea he played at, and was named the man-of-the-match in England's victory. Roby returned to international rugby league when he was selected to play for England against France in the one-off test. In 2011, Roby played in the 2011 Rugby League Four Nations, and was part of the team that lost the final to Australia. In 2013 Roby was named in England 2013 World Cup squad but lost in the semi-final in the dying seconds to New Zealand. After missing out on the 2014 Four Nations, Roby was selected in Englands 24-man squad to take on New Zealand in an end-of-year test-series. In a warm up game before the first test against the Kiwis, England took on France in a test match. Roby scored two of England's 15 tries in their romp over their opponents and went on to beat the Kiwis 2–1. In October 2017 he was selected in the England squad for the 2017 Rugby League World Cup.
