Rosie O'Donnell is calling out Kevin Spacey for allegedly having a rep as a predator in Hollywood, akin to Harvey Weinstein ... saying everyone in Hollywood knew.

Rosie took to Twitter Monday to directly slam Spacey for not remembering an alleged attempt at molesting then-14-year-old Anthony Rapp ... and she didn't mince words.

u don't remember the incident - 30 years ago? - fuck u kevin - like Harvey we all knew about u - I hope more men come forward @KevinSpacey @Rosie

She tweeted ... "f*** u kevin - like Harvey we all new about u - I hope more men come forward @KevinSpacey." Rosie added ... "no one knew details - like harvey - but u knew both were creepy men with reps that said so."

no one knew details - like harvey - but u knew both were creepy men with reps that said so - @Rosie

As we reported ... Spacey came out as gay in his statement addressing Rapp's allegations. Other celebs have blasted him for choosing such a moment to embrace his sexuality.