Roger Dunn's career as a professional scriptwriter began in the early to mid-1970s with Crawford Productions. Among the earliest shows to include his name in the credits are The Box (1976; The Sullivans (1976-1977), for which he was also script editor; and Skyways (ca. 1979).
In the early 1980s, he adapted children's fiction for film and television. In 1982, he adapted David Burke's novel Come Midnight Monday as the ABC television series Come Midnight Monday. In 1984, with Graeme Koetsveld, he wrote the screenplay for The Fire in the Stone, a feature film adaptation of Colin Thiele's children's story of the same name.
During the 1980s, Dunn also provided episodes for such popular series as A Country Practice (1982-1984), The Flying Doctors (1986), Professor Poopsnagle's Steam Zeppelin (1986), Return to Eden (1986), and Mission: Impossible (1989).
In the 1990s, Dunn wrote episodes for such television series as Halfway Across the Galaxy and Turn Left (1994) Blue Heelers (1997-1999), Thunderstone (1999), and Chuck Finn (1999).
Between 1999 and 2000, he wrote numerous episodes of long-running soap opera Neighbours.