In a nine-minute video posted on his Instagram account, Evra called Rothen, who he played alongside at Monaco, a "piece of sh*t" and that he was "always a salty pr*ck".
After the win in Paris, that was sealed after Marcus Rashford's stoppage-time penalty, Evra posted clips of himself celebrating and mocking PSG, including alleged homophobic slurs.
"I'm not homophobic, you know who I am [...] I love everyone," he said. "If I offend someone or I hurt someone, I really apologise.
"But you know it's not my intention, they're just trying to put me down. I understand about the equality; you have to be free whatever you do in life.
"I would never judge anyone. My mum raised me and educated me that way."
And Rothen has now confirmed to RMC Sport that he has filed a legal complaint against Evra: "I had decided well before [the investigation opened by the Paris court], with my lawyer, to make a complaint."
PSG's stance has also been one of condemnation against Evra having previously issued an official statement in support of equality campaigning organisations Rouge Direct, Sportitude and SOS Racisme.
It read: "PSG strongly condemns Patrice Evra's homophobic insults towards the club, its representatives, and its former player [Rothen], in a video broadcast across social networks.
"These remarks deeply shocked a club very attached to the values of respect and openness towards each other.
"The fight against homophobia and all forms of discrimination is at the heart of PSG's actions and values, which has worked alongside Rouge Direct to fight homophobia, as well as Sportitude against all forms of racism.
"PSG will support any initiative taken by associated partners Rouge Direct, Sportitude and SOS Racisme."
Evra had watched the second-leg tie in Paris from the stands with suspended Old Trafford star Paul Pogba and posted his first video inside the stadium within minutes of United's comeback win.