Of Samoan descent, Roberts is the cousin of soccer players Tim Cahill and Chris Cahill. He was educated at John Therry Catholic High School, Rosemeadow, and Patrician Brothers' College, Fairfield, alongside Sharks centre Dean Collis.
Joining the Canterbury-Bankstown Bulldogs in 2006 as a five-eighth, Roberts was originally recruited from Western Suburbs Magpies before became a regular member of the NSWRL Premier League team. In 2007, he has started in halfback in the early rounds due to injury to regular playmaker Brent Sherwin. With Sherwin's return from injury and form, Roberts was shifted to five-eighth.
He made his second international appearance for the New Zealand Kiwis on Friday 20 April at the 2007 ANZAC Test against the Australia national rugby league team in Brisbane.
He was named in the New Zealand and Samoan extended training squads for the 2008 Rugby League World Cup. In the end he was selected in the Samoan squad for the tournament.
5 years later he was selected for Samoa in April 2013, for a test match against Tonga in Penrith, New South Wales. Later in the year he was selected for Samoa again, but this time for their 2013 Rugby League World Cup campaign. He featured in all four games that the Samoans played, scoring two tries. He scored one try against heavyweights New Zealand in an entertaining 42–24 defeat. He scored his second try in Samoa's 38–4 thrashing of The Kumuls.
On 17 May 2011 Roberts signed a two-year deal with The Parramatta Eels.
On 23 January 2014, it was announced he had signed on with the Melbourne Storm for the 2014 season. In round 1 of the 2014 NRL season, Roberts made his début for the Storm against the Manly-Warringah Sea Eagles.
On 7 October 2014, Roberts was selected in the Samoan 24 man squad for the 2014 Four Nations series.
On 7 July 2014, it was announced that Roberts signed a contract to play for the Super League club Castleford Tigers in 2015.
He played his first Super League game against the Catalans Dragons in the second round of the season. He scored his first Super League try against the Warrington Wolves in round 9.
Roberts scored in Castleford's opening home fixture against Wakefield in round 2 of the 2016 season.
As of 25 September 2015