Date of birth
Midfielder joined Pompey from Chesterfield for an undisclosed fee in June 2015.
The move saw him join former Accrington team-mate and Spireites boss Paul Cook at Fratton Park, featuring 35 times in the league in 2015/16 and scoring eight times.
Last season he played a pivotal role in the Blues march to the Sky Bet League Two title, with 10 goals in 41 appearances.
The former Liverpool youth player started his professional career in Wales before signing for Stanley in 2005.
He moved on to play for Ipswich, Huddersfield and Swindon, arriving at Chesterfield in the summer of 2013 and helping them win promotion from the fourth tier.
Roberts scored 20 goals in 89 appearances for the Derbyshire club, including the winner against Fleetwood in May 2014 that secured the League Two title.