Johnson told BBC Radio Cambridgeshire: "Having a director of football is a big reason for me wanting to come here.
"A lot of the stress that managers get is when they have to start dealing with agents and contracts."
Fry has worked as director of football at London Road since selling the club to Darragh MacAnthony in 2006.
However former boss Jim Gannon expressed concern over Fry's role and level of responsibility during his spell with the club.
Gannon said: "I'm not in charge of the overall football department as I see it. It's about defining the roles between the manager and the technical director.
"It's about who is ultimately responsible for the performance in the football department, who's responsible for recruiting, who's responsible for players leaving, who's responsible for how the budget is spent."
Johnson has said he does not want the hassle of negotiating with players at this stage of his managerial career and their agents and Fry believes they can work as a team.
"Gary is the manager, he indentifies the players he wants and I try to go out and get them with the help of the chairman," he said.
"He identifies who he doesn't want and I try and get rid of them. That's my role, it's simple really."
Meanwhile, Posh have recalled striker Ben Wright from his loan spell at Barnet.
Source: BBC Sport
Source: BBC Sport