On the appointment, Rooney said: "I am sad to see Pete leave the club. He is someone I have worked with very closely throughout my managerial career having first met at Derby County and he has also been a close friend.
"Mike is someone I know well having worked with him when I was a player at Manchester United and he has vast experience at the highest level of football.
"I am really pleased to bring him to Argyle and look forward to seeing him get to work immediately."