In a week when Romero slammed the board publicly for an underwhelming winter market, he was sent off in defeat at Manchester United. It means the Argentine won't be seen in domestic action again until March 15.
Keown told talkSPORT, "We sat here and argued about Aubameyang a few years ago and I was trying to defend him because I thought, ‘ok, let’s keep the player at the football club’.
"Maybe you’re cutting your nose off to spite your face and there may be a feeling about this with Romero right now.
"But actually if you want to change the culture of that football club, and there’s a serious problem with the culture at that football club, maybe this is the one to say, ‘do you know what? He doesn’t play for our football club again. We’re making a change.’
"I know he’s a big commodity and it’s a gamble but it’s a change of direction and a change of culture because I would say, if you see this on the outside, on the inside it’s even worse.
"On the inside, his behaviour around the players is not good for the next generation and therefore big decisions have to be made around this player. He’s at a crossroads in his career."
The former Arsenal defender added: "I think this guy is a top player but there’s something there that sparks and he’s off the pitch.
"It can’t continue. He has to make that decision otherwise he walks at the end of the season."