Leeds head coach says he is devastated.
Rosler told BBC Radio Leeds that he regarded Pearson as a friend, and does not know the plans of his superiors going forward.
Leeds announced via their official website that Pearson has left the club, with an open letter from the now former chief executive citing personal reasons.
Rosler said: "It's a very big surprise and a big blow. Adam came to the club at the same time (as myself), we all had developed in a short time a close relationship.
"I call him a friend, and I'm devastated that he left us. I wish him all the best, I enjoyed every minute he worked with us. I hope to see him again.
"I have no idea what the plan is going forward. I heard the news, and concentrated on preparing the team today."
The timing could not have been worse, with the announcement made shortly after Leeds had suffered their first defeat of the season in the Championship, suffering a disappointing 1-0 loss at home to Ipswich Town.
It leaves Leeds with only one win in the league this season, and in the bottom half of the table.
Pearson had been seen as a stabilising figure behind the scenes, and Rosler's comments about the uncertainty which currently exists, also illustrates the worry Leeds fans may have about off the field matters overshadowing another season.
More to follow...