The 24-year-old, whose senior career began at Monaco, spent last season on loan at Saint Etienne where he netted four times in 19 appearances.
Ian Holloway has already added two wingers to his squad this summer in the shape of Jerome Thomas and Elliot Grandin, but Rousselot says that the Eagles are also chasing Mollo.
"Talks are starting to heat up," he told Nancy's official website.
"Crystal Palace are expected to return on our proposal, then it requires all parties to meet.
"Two German clubs are also interested while Olympiakos have not abandoned this issue."