Mr. Fentress is a native of Evanston, Illinois. He began his career while still in college, working in New York during the summer for Broadway producer Arthur Cantor, who introduced him to film director Frank Perry. Robert went to Alabama to work as an assistant to Mr. Perry on Truman Capote's A Christmas Memory, and then returned to New York to work with him on pre-production for The Swimmer, starring Burt Lancaster. Robert then came to Los Angeles to attend the Southern California Film Institute, where his short film Mary C Brown & the Hollywood Sign played at the Los Angeles International Film Festival and on KCET-TV (PBS) in Los Angeles.

During the 1970's, Robert worked in public relations, foreign film distribution, and radio, where he co-produced the highly acclaimed 12-hour syndicated radio special, Project Sinatra. During the late 1970's, Robert started a long-term association with writer-producer Ronald Shusett as Mr. Shusett was in pre-production on Alien. In 1981 they co-produced Dead & Buried, co-written by Mr. Shusett. Next, they began the journey of developing Total Recall, first with Dino DeLaurentis, and then with Carolco, where it was produced and released in 1990 with a worldwide box office gross of $261 million.

In 2002, Robert joined forces with Ilya Salkind and is co-executive producer of Alexander the Great from Macedonia. Mr. Fentress is on the Board of Directors for The Ilya Salkind Company.