It is Rooney’s first role since he was sacked by Birmingham City on 2 January after a disappointing reign of less than three months in which he lost nine of 15 games.
Blues, who were in the Championship play-off places when Rooney took over, were relegated to League One earlier this month.
The Pilgrims job is a fourth head coach role for Rooney – who was England’s top scorer with 53 goals until his mark was beaten by Harry Kane in March 2023.
He was Derby County boss during a period of financial difficulties.
Rooney guided the Rams to Championship survival in May 2021 in his first season in charge, but left a year later following the club’s relegation after Derby had been docked a total of 21 points for their financial problems.
He spent 15 months as boss of DC United in the United States, but left last October to take on the Birmingham job, having failed to guide the Washington-based side to the Major League Soccer (MLS) play-offs.
First-team coaches Kevin Nancekivell and Simon Ireland, and goalkeeping coach Darryl Flahavan will form part of Rooney’s backroom staff, with further additions to be made in due course.
