The Blaugrana president is a big fan of the Belgium international, who is currently in his third season on loan with Atletico Madrid.
The 21-year-old has impressed during his time in Spain, which has led to suggestions he is being ear-marked as Valdes' replacement in the summer.
"He is a great goalkeeper, he is very good and I like him a lot," Rosell told reporters.
Courtois is still to feature for Chelsea following his £5million move from Genk in June 2011, with Petr Cech still the No.1 at Stamford Bridge.
Despite going public with his views on Courtois, the Barca supremo still hopes that he can persuade Valdes to sign a new contract, despite him stating his time at the club is coming to a close.
"Up until the last moment we will try to keep Valdes at Barca, but it will be difficult," Rosell continued.