Van Gaal was officially unveiled as the United boss on Thursday less than a week after finishing third with the Netherlands at the World Cup.
Despite LVG's preoccupation with his national side in Brazil, the Red Devils have already splashed out around £60 million on Ander Herrera and Luke Shaw.
And now Rooney has called for his teammates to shrug off the deeply disappointing performances from last season and show their new manager just exactly what they can do in the coming campaign.
In an interview with The Sun, the England international said: "We all have to go out and show what we can do. We have to show him every day in training what different qualities we have got as players and a team.
"Everyone wants to impress the new manager so that is what we are all aiming to do. We will try to put what we are doing in training into the games.
"Obviously, we have a manager with new ideas so we have to try to train well and make sure we are listening to what he wants to do and take that on to the pitch. We have to show him what we can do.
"I've only had one session but the preparation has been really good. I'm just looking forward to getting more sessions in before our first game."
Despite United's harrowing campaign that seen them finish in their lowest-ever Premier League position of seventh, Rooney still managed 17 goals in 29 appearances and was rewarded with a new contract in February, worth around £300,000 a week.
Speculation was rife that Rooney was to be handed the captaincy following the signing of the new contract but Van Gaal has since indicated that he will take his time over the appointment of a new skipper.
Van Gaal takes charge of his first match in the early hours of Thursday morning when the Red Devils take on LA Galaxy.