The 21-year-old signed a one-year contract with the West Yorkshire outfit in June of last year.
However, according to The Irish Sun, the Republic of Ireland Under-21 international goalkeeper will leave Leeds in the summer after failing to make the breakthrough.
Interestingly, Grimes was in the Leeds academy when Neil Warnock was in charge of the first team.
Warnock is in charge of Rotherham at the moment, but his current contract runs out in June 2016.
According to TEAMtalk.com, the former Sheffield United boss will sign a new deal with Rotherham.
The Millers avoided relegation to League One, finishing as many as nine points above the Championship bottom three this season.
As for Leeds, the West Yorkshire outfit endured yet another disappointing campaign in the Championship, ending up as low as 13th in the standings.