Chelsea’s losses to PSG in both legs of their Champions League tie were sandwiched in between them being beaten 1-0 at home by Newcastle United.
The defeat by the Magpies left the Stamford Bridge club sixth in the Premier League – one point behind fifth-placed Liverpool – and out of the Champions League qualification spots with eight games left.
“Every manager goes through difficult weeks,” said Rosenior.
“I’ve had challenging periods before. I’ve lost games in many jobs, like all managers have done. We need to find a way to fight at Everton and come through a difficult period.”
He added: “You want to be in the Champions League. It makes everything clearer, not just from a financial point of view. This club deserves to be in the Champions League. That’s the target.”
Rosenior, who will be without defender Trevoh Chalobah for “around six weeks”, also said the social media criticism of him passing a note to his players when 8-2 down on aggregate against PSG “doesn’t bother me”.
“The reality is that I have to help this club win matches. If I don’t, if I breathe wrong or sneeze wrong, people will talk about it. It doesn’t affect me. It’s my job to be aware. Am I surprised? No,” said the Blues boss.
“In terms of the game on Tuesday, it completely didn’t go the way we wanted it to.
“Me handing out a note is not a reflection of my message not getting across to the players.”