Mevlut Erding capitalised on a mix-up between experienced goalkeeper Carroll and defender Chris Baird to score the only goal in Adana in first-half injury time.
O'Neill was left to reflect on another frustrating evening as his depleted side were unable to hit back in their first game since the manager signed a new contract.
"Roy Carroll held his hands up. He knows himself he made the wrong decision for their goal and he's disappointed in that," O'Neill said.
"Roy called for the ball and Chris Baird left it for him. The centre-forward just continued his run and got a toe to it.
"Chris did the right thing in thinking Roy was coming to take it but that wasn't the case."
The former Shamrock Rovers boss warned his players they must cut out the errors if they are to avoid further disappointment in the future.
"This team has suffered quite a few injustices in terms of not getting what they deserve from games and this was probably another example of that," he added.
"We've have come out on the wrong end of a sequence of bad decisions, bad goals, deflections.
"We've had a lot of things to deal with and we've not had anything that I can think that has really gone for us in any game.
"It's basically the last kick of the half. Roy knew he was coming off at half-time but I don't think he was thinking about having a shower at that moment.
"People make decisions and Roy made a bad one."
