Barca won 4-0 at the Santiago Bernabeu, with stand-in goalkeeper Andriy Lunin also not escaping Roncero's wrath in the absence of Thibaut Courtois.
The AS football chief and Real Madrid fan declared: "They gave us a hard time in the second half. They got the better of us tactically. The defence was a disaster.
"There is so much difference with Courtois... I put a lot of blame on Mbappé. They brought in the supposed best player in the world so that he could appear and make the difference these days, and (Robert) Lewandowski made the difference at 36 years old. (...).
"This is Madrid, not Paris, which is where you can see the Eiffel Tower. (Carlo) Ancelotti will have his responsibility, but he cannot make a supposed world number one star miss goals that maybe not even my son would miss."