Many of Loomis' authors had worked with him for decades, including Maya Angelou, who wrote 31 books under his editorship, beginning her first autobiography, I Know Why the Caged Bird Sings (1969). His authors' loyalty to him and him to them was almost legendary. Loomis represented "the classic mold of the editor" and according to Random House, he "embodied the ideal of an old-fashioned editor: understated, but uncanny; polite, but persistent". As Angelou has said, Loomis "knows what I hope to achieve in all my work. I don't know anybody as fierce, simply fierce, but he's as tender as he's tough." He was well known as a mentor to editors and writers in all areas of the publishing industry.
Other notable authors who have been edited by Loomis include Calvin Trillin, Edmund Morris (who wrote Dutch, the "controversial" biography of US President Ronald Reagan), Shelby Foote, Jonathan Harr, and anchorman Jim Lehrer. He edited the Vietnam war epic, A Bright Shining Lie, by Neil Sheehan, which won both the Pulitzer Prize and the National Book Award, and in 1998, the novel he edited for Pete Dexter, Paris Trout, earned the National Book Award, "an unprecedented feat in editing."
Loomis and author William Styron had known each other since they were both students at Duke University, where Loomis was Stryon's editor at Duke's student magazine. Loomis went on to edit all of Stryon's books except Lie Down in Darkness, his first novel.
- Italie, Hillel (2011-05-06). "Robert Loomis, Editor of Styron, Angelou, Retires". The Washington Times (Associated Press). Retrieved 2011-12-22.
- Arnold, Martin (2001-04-12). "Making books; Familiarity Breeds Content". The New York Times. Retrieved 2007-11-12.
- Smith, Dinitia (2007-01-23). "A Career in Letters, 50 Years and Counting". The New York Times. Retrieved 2007-11-12.
- Lesley, Stahl (2004-06-09). "Morris: 'Reagan Still a Mystery'". CBS News.com. Retrieved 2007-11-13.
- "Where the Written Word Reigns". Duke Magazine 93 (3). May–June 2007. Retrieved 2007-11-13.