Rosler believes that Al-Habsi has been forced to raise his game due to the competition that he has for a starting berth.
"To cement his place, after Scott came back from injury and with Lee Nicholls being available every training session, shows the level of performance Ali has delivered since I walked through the door," Rosler told TEAMtalk.
"Ali took his chance and I think it would have been unfair to Ali and sent the wrong signals to the squad, when we talk about fair competition, to take Ali out.
"I am very happy with the goalkeepers. I think I probably have the strongest goalkeeping department in the league with three top goalkeepers. It speaks volumes that Ali has cemented his place as number one."
Wigan currently sit fifth in the table.