Sancho shone last season in the German Bundesliga and emerged as one of the most exciting youngsters in world football.
His fine form led him to attracting heavy interest from United as Ole Gunner Solskjaer looks for some creativity in his team.
However, Rooney, who is Man United’s record goalscorer advised the player not to join his former club.
He told Bild, “Now Jadon has to ask himself whether he would get the playing time he gets in Dortmund when he moves to England, or would he just sit on the bench?
“Playing time is so important for a young player like Jadon, so if he gets the most playing time in Dortmund, he should stay there.”
The England youth international scored 13 times and created 19 assists in all competitions for Dortmund last season.