The Dubliner arrived at Crabble in June 2019 after spending the previous season with League Two side Colchester United.
Rooney joined Championship side Millwall in July 2016 having spent his early senior career with League of Ireland clubs St Patrick’s Athletic and Bohemians, making his Lions’ debut away to Luton Town in the Football League Trophy four months later.
A two-month loan spell followed at National League side Torquay United where he made seven appearances in all competitions, scoring once.
Rooney, who can also operate in midfield, moved to Colchester in January 2018 and had loan spells with National League side Bromley and National South team Billericay Town prior to his move to Crabble.