The 32-year-old joined Bradford on a two-year deal from Tranmere last summer, but has agreed a mutual termination at Valley Parade.
He scored three goals in 35 appearances for the Bantams and manager Stuart McCall is not surprised McLaren is heading back to League One.
McLaren has been offered a two-year deal by new Rovers chief John Barnes and it is understood he will take a sizeable pay cut.
"Macca is a very, very talented footballer, no doubt about it," McCall told the Telegraph & Argus.
"He will be the first to admit he didn't reach the heights he hoped for, especially at home, where teams came and clamped down on him with three in the middle.
"It reminded me of my time at Rangers with Paul Gascoigne. I'm not comparing the two as players, but the scenario was very similar, with Scottish Premier League teams flooding the midfield to keep him quiet.
"Macca had some excellent games for us, but then again some very quiet ones as well. But I'm not surprised that two or three clubs from League One had been on to us about him.
"I'm disappointed to lose him, as I was about Graeme Lee. I know it had to be done from the budget point of view, but both lads will be missed in the dressing room and on the park."