Although Rovers are yet to officially confirm the move, Gerrard's prospective switch to the Keepmoat Stadium has been widely reported since Dickov was handed the reins with the Championship newboys last month.
Gerrard played for Latics between 1991 and 1996 and joined their staff three years ago, serving as joint-caretaker manager alongside Tony Philliskirk in the wake of Dickov's January departure.
Oldham manager Lee Johnson told his club's official website: "It is the first disappointment since I have been here.
"I am disappointed to lose Paul as we got on well and I enjoyed working with him.
"There are no hard feelings and I wish Paul all the best at Doncaster which is a great club.
"I am shrewd and have made provisions to bring somebody in as good as Paul, if not better."