Milnes was opera critic of Harpers and Queen (1970–90), opera critic of The Spectator (1988–90), Evening Standard (1990–92), and Chief Opera Critic The Times (1992–2002). He was associate editor of Opera from 1976, deputy editor from 1984, and editor between 1986–99. There he honed his reputation as a "trenchant and entertaining writer, with a strong background in literature and theatre, and wide musical sympathies". In his final editorial for Opera, Milnes wrote "Thank you to all of those who have written in outrage cancelling their subscriptions, and then not done so. Thank you to all readers for being so patient with my bêtes noires. I know I’m wrong about surtitles (like hell I am) and they’re here to stay. So are sponsors and their lordly, impertinent ways. Call me old-fashioned, but I don’t really feel that a century that starts with Lilian Baylis and ends with Chris Smith is one that has seen a lot in the way of progress".
Milnes contributed entries on Massenet and his operas in the Grove Dictionary of Music and Musicians. He was consultant editor for the Viking Opera Guide, and revised and updated A Concise History of Opera in 1987. He was a contributor to Opera on Record Vol 1 (Carmen), Vol 2 (Thais and Don Quichotte) and Vol 3 (The stage works of Weill).
For BBC radio he was a regular on Building a Library in Record Review; in Just the part and In Repertory he talked to opera singers about particular roles they have made their own, and in 2001 introduced a 14-part series Performing Verdi.
He is a Knight of the Order of the White Rose; in January 2002 he was awarded an OBE for services to journalism and music.
- Rodney Milnes. New Grove Dictionary of Opera. Macmillan, London and New York, 1997.
- Adam, Nicky (ed). Milnes, Rodney. In: Who's Who in British Opera. Scolar Press, Aldershot, 1993.
- Editorial "Ring in the new". Opera, December 1999, p1387.
- Radio listings for Just the Part series Accessed 29 May 2011
- Radio listings for In repertory series Accessed 29 May 2011