Rossi, 82, passed away Sunday at a hospice here. He had been suffering from cancer prior to his death, reports femalefirst.co.uk.
His longtime comedy partner Marty Allen told the Las Vegas Sun newspaper: "What can I say? I am totally at a loss for what has happened. We had a lot of great years together... He was a wonderful talent and a wonderful man".
Veteran entertainer Wayne Newton said: "He was a great man and a great friend. He will be missed dearly."
Penn Jillette, of illusionist duo Penn and Teller, added: "Teller and I saw Allen and Rossi in Atlantic City in the '80s, and they were wonderful. There are things that only people who have been part of a comedy team know. I will miss Steve's calls to talk about those things".
Allen and Rossi rose to fame in the 1950s and were popular for shows like "The Tonight Show With Johnny Carson" and "The Merv Griffin Show", while they also appeared with The Beatles on "The Ed Sullivan Show".
They also spent several years touring with Nat King Cole.
Allen and Rossi parted ways in 1968, but reunited on a number of occasions over the years. Their last tour together was in 1994.