Roberts' contract is set to expire and the Championship club have taken the decision not to offer the 35-year-old a new deal.
Saturday's game against the Lions will be his final appearance for the Rams.
Manager Nigel Clough told the club's official website: "Gareth has been incredible for the three years he has been here and the supporters have acknowledged that.
"Physically he is in a great shape, even in pre-season when he came back in July last year he put a lot of the younger lads to shame.
"He has been a wonderful servant for three years and we will be doing all we can to help secure his future elsewhere.
"He has been helping out with the coaching at the academy as well, so there is a possibility that he might still be around the place."
Roberts joined Derby on a free transfer in the summer of 2010 following his release by Doncaster.
His only goal for the Rams came in a 2-1 win against his former team in March 2012, and his contract was extended by a further year shortly afterwards.
During the current campaign, Roberts has made 31 appearances for Derby and made his 600th senior club appearance against Peterborough at London Road in October.