Axford is 2-5 with a 4.86 ERA. His last save preserved a 2-1 win over Arizona on July 2.
"I think when he gets on the mound that same confidence that he had last year is not there now," Roenicke said. "It can't be. But he's still very confident in what he does. He still believes that when he comes out there and there's a save situation, he's going to get the job done.
"But he needs to string together a few really good outings in a row to get that same confidence that he had last year. I think right now, in this series, we're still looking at 'Ax.' That can change. We really haven't talked about that changing yet."
Axford did not appear and there were no save opportunities in the first two games at Houston.
"I know [Francisco Rodriguez] went through a stretch where he wasn't himself, either," Roenicke continued. "But I think if 'Frankie' is himself and there's a point where 'Ax' isn't coming around like he was, we certainly would think about it. Right now, we're not talking about it."