Rossi "has left the stage," his website reported, surrounded by friends and family that included his wife, Karma. He had cancer and died at a hospice, according to the Hollywood Reporter.
Allen and Rossi joined forces in 1957 and appeared dozens of times on The Ed Sullivan Show, including three times with The Beatles.
Steady performers in comedy clubs and Vegas casinos, they released a string of comedy albums, appeared on game shows and were regulars on The Tonight Show With Johnny Carson and The Merv Griffin Show before splitting up in 1968.
A native of New York, Rossi at age 16 received a scholarship to Loyola Marymount in Los Angeles and earned his bachelor's degree. He sang and toured with Mae West before teaming with Allen.