The French team had already reached an agreement with the American Lance Armstrong, who revealed earlier this month that he had testicular and abdominal cancer, to be their No 1 rider.
Cofidis said they would still welcome Armstrong, currently undergoing treatment, if he were fit enough to join them but added they had to find somebody to replace him.
Rominger, a former world hour record won the Tour of Spain three times in a row from 1991 and 1993 and the Giro in 1995, was looking forward to a new challenge before retiring at the end of 1997. He rode for Mapei last year.
The 35-year-old from Switzerland proved he still had plenty to offer this year by taking third place in both the Vuelta and the time trial event at the World Championships.Reuse content