Like the many thousands each year who pass under that mocking legend "Arbeit Mach Frei", Rooney was left incredulous at the sheer inhumanity of a site which brutally put 1.1million Jews to their deaths, 80% within two hours of their arrival.
But as those who experienced it first hand get fewer, so the education process needs to be reinforced, and Rooney said: "Kids nowadays are interested in footballers. I am sure that will get them interested. I am sure all of us who were there will speak of what we have seen. If a few more people understand it that's good."
Accompanied by Phil Jagielka, Joe Hart, Leighton Baines, Theo Walcott, Andy Carroll and Jack Butland, Rooney was struck most by a picture hanging in a building at Auschwitz, depicting a scene from nearby Birkenau.
No-one is quite sure who it was. It might have been the infamous SS officer Heinz Thilo but it is too grainy to be certain.
Yet there is no doubt about what it depicts.
With a flick of the finger, an old man is told to join a queue.
He has just got off a train, one of thousands, its origin unknown. Clearly he is not someone capable of working a 10 hour day on a couple of slices of bread.
The decision is easy. The finger flicked to the mass of people to the right. He does not know it but this unnamed old man is 400 yards and two hours away from his death.
"That guy who made all the decisions, whether they lived or died," said Rooney softly, his words delivered with total disbelief. "He's probably gone home after that, listened to music, had dinner with his family, as if nothing had happened. It's crazy."