 After defeating Fleetwood Town over two legs in the Football League Trophy area final, Roberts had the chance to play at Wembley Stadium for the second time in three years, however the Spireites succumbed to and 3–1 defeat by Peterborough United.On 17 June 2015 Roberts joined Portsmouth on a three-year deal, stating that manager Paul Cook, Roberts' manager at Chesterfield, was the main reason for him signing for the club.He scored a stunning free kick against Morecambe to rescue a point.