Rosenior, 42, took over at Chelsea in January but oversaw just 23 matches before being sacked in April by the Premier League giants.
"We joined the club in the middle of a season and a difficult moment, and I have many lessons I've learned," Rosenior told reporters at his first press conference since being named Paris FC boss.
"There are things that I definitely could have done better and things I could have taken accountability for but there are also good things in what we did as well."
However, the Englishman said he bore no ill will to Chelsea, nor to his successor, Xabi Alonso.
"I wish them all the best in the future. I think they have a fantastic manager, Xabi Alonso, now, and I will look out for their results," he said.
"But those lessons that I take away from Chelsea, we will put into this job and hopefully we'll help this club be a very, very big club in world football as well."
Prior to taking over at BlueCo flagship club Chelsea, Rosenior made his name at another of the consortium's entities, French top-flight side Strasbourg.
"(Ligue 1 is) a fantastic league. I said that when I left for Chelsea. I feel like myself and the staff have joined such an exciting project, where the potential is so big," he said.
"It was something I couldn't say no to."
Paris FC, owned by the LVMH luxury group, finished 11th in Ligue 1 last season.