The free-agent full-back made 35 appearances in all competitions for the Whites following a free transfer from Bristol City in the summer of 2017.
Despite being a first-team regular for most of his first season, the 30-year-old fell out of favour following a red card against QPR in February 2018, starting only three more games that season.
He was in the side that beat Nottingham Forest on the final day to secure Championship survival but failed to make an impression last season, making just four appearances and only one start in the league.
Little helped Bristol City to the Football League Trophy and promotion in 2015 and has now returned to the South West, where he will line-up against Wanderers in League One.
Rovers boss Graham Coughlan said; "Mark is a player that should be playing at a higher level, he adds good quality and is a real all-rounder so we are delighted to bring him to the club.
"He's got two promotions on his CV, an abundance of experience in the leagues and he knows what it takes to get out of this division."