The United striker won a penalty for England, following a tussle for possession with defender Bostjan Cesar.
Koren said: “This week there has been a lot of talk about diving, about Arsenal’s Eduardo.
“Today I think Rooney went down a bit too easy and let’s see if someone will say something against him.
“My personal opinion is the referee was under a little bit of pressure because of the crowd and the England team. That penalty was a bit too easy.”