The £105m facility was officially opened on Tuesday by the Duke and Duchess of Cambridge and will be the base for England's 24 teams from junior to senior level.
The Three Lions squad have been training at St George's Park ahead of their World Cup qualifying matches, and Rooney is already impressed.
"The facilities and training pitches here are brilliant," said Rooney.
"It's a great platform for the younger players –the next level of players and coaches.
"All in all it will benefit the whole of the England team in years to come and especially the younger players."
Rooney made his England debut in 2003.