United's all-time leading goalscorer has told his former club to ignore the enticement of a big named signing like Bale or Cristiano Ronaldo to focus on rebuilding the club.
"The first thing Ole has to do is build the squad and I don't think bringing in one or two players for £100m is going to help the players already there," Rooney told the BBC.
"He's better spending £30million to 40million on players with potential and building the squad around those five or six players.
"You could bring in players in Ronaldo, Messi, Ramos or Bale but it's going to cost you £350million and you'd get two years out of them and you've written that money off.
"The club needs to rebuild with younger players but they need to be good enough and I think the fans will understand that they are probably not going to compete for the Premier League next year.
"Let Ole have that time to build a team for the next two or three years that are going to compete at Premier League and Champions League level.