Rozehnal said: "We were not going to start playing well immediately and in the first season win three trophies.
"We all need more time because everyone makes mistakes, and you have to learn from those mistakes.
"You have to keep going and if we don't win something this year, I promise the supporters we will do our best to win something next year, or to qualify for the Champions League or the UEFA Cup.
"That's what we want and what the supporters want."