During the 1990s, Roberts was associated with the popular range of Doctor Who spin-off novels published by Virgin Books. He contributed several novels to both their New Adventures and Missing Adventures ranges of Doctor Who fiction. He also wrote some Cracker novelisations for Virgin.

He continued to be associated with Doctor Who in the 2000s, penning several feature articles and comic strips for Doctor Who Magazine, co-writing audio plays and short stories based on the series with Clayton Hickman for Big Finish Productions, and in 2005 writing another Doctor Who novel, Only Human, based on the characters from the new series launched that year, for BBC Books' New Series Adventures range. A further novel, I am a Dalek, was released in 2006 and featured the Tenth Doctor. I am a Dalek is part of a Government "Quick Reads initiative". He also co-wrote The New Gods with Rebecca Levene, the first Tomorrow People audio drama for Big Finish.

Roberts appeared as a contributor to the documentary Serial Thrillers, exploring the popular Philip Hinchcliffe era of Doctor Who between 1975 and 1977, which featured as an extra on the 2004 DVD release of the serial Pyramids of Mars.

On 25 December 2005 a special 'interactive' mini-episode of Doctor Who written by Roberts, Attack of the Graske, was broadcast, and can now be accessed on the BBC website (only available to UK Broadband Users). Roberts also wrote a series of "TARDISODEs", short videos available online and via mobile phones promoting the 2006 series of Doctor Who.

He has written three full episodes of Doctor Who, "The Shakespeare Code" in 2007, "The Unicorn and the Wasp" in 2008, and "The Lodger" in 2010.

Roberts also co-wrote, with Russell T Davies, "Invasion of the Bane", the pilot episode of the Doctor Who spin-off series The Sarah Jane Adventures. He wrote two two-part stories for the full series of The Sarah Jane Adventures, which began broadcasting in the autumn of 2007, and another two two-part stories for the 2008 series.

Roberts co-wrote with Davies again for the first of the 2009 specials of Doctor Who, "Planet of the Dead".

Roberts has worked on some of the most popular British soap operas, including Channel 4's now-defunct Brookside as a scriptwriter (1999—2003), and as a story associate on ITV's Coronation Street in 1997. In 1998 he worked as a script editor on ITV's other long-running soap, Emmerdale, moving across to write several episodes himself the following year.

In comedy, Roberts has worked in collaboration with The Fast Show writer and performer Charlie Higson on the sitcom Swiss Toni, a spin-off from The Fast Show. He also collaborated with Higson on scripts for the second series of Randall & Hopkirk for BBC One in 2001.

Roberts has also contributed sketches to the Five sketch show Swinging.

• The Highest Science (Doctor Who New Adventure, 1993)
• Tragedy Day (Doctor Who New Adventure, 1994)
• Zamper (Doctor Who New Adventure, 1995)
• The Romance of Crime (Doctor Who Missing Adventure, 1995)
• To be a Somebody (Cracker novelisation, 1996)
• Best Boys (Cracker novelisation, 1996)
• The English Way of Death (Doctor Who Missing Adventure, 1996)
• The Plotters (Doctor Who Missing Adventure, 1996)
• The Well-Mannered War (Doctor Who Missing Adventure, 1997)
• Only Human (Doctor Who New Series Adventure, 2005)
• I am a Dalek (Doctor Who New Series Adventure, 2006)

Short stories in:

• Lost Property (1995)
• Consequences (1996)
• More Short Trips (1999)
• Short Trips and Sidesteps (2000)
• The Muses (2003)
• Doctor Who Annual 2006 (2005)
• The Doctor Who Storybook 2007 (2006)

Television scripts:

• Emmerdale (several episodes, 1999)
• Springhill (storyline writer)
• Brookside (contributing writer, 1999—2003)
• Randall & Hopkirk
• "Whatever Possessed You?" (co-written with Charlie Higson, 2001)
• "Painkillers" (additional material by Mark Gatiss and Jeremy Dyson, 2001)
• Swiss Toni (staff writer, 2003)
• Swinging (staff writer, 2005)
• Doctor Who
• "Attack of the Graske" (interactive episode, 2005)
• "The Shakespeare Code" (2007)
• "The Unicorn and the Wasp" (2008)
• "Planet of the Dead" (co-written with Russell T Davies, 2009)
• "The Lodger" (2010)
• The Sarah Jane Adventures
• "Invasion of the Bane" (co-written with Russell T Davies, 2007)
• Revenge of the Slitheen (2 parts, 2007)
• Whatever Happened to Sarah Jane? (2 parts, 2007)
• Secrets of the Stars (2 parts, 2008)
• The Temptation of Sarah Jane Smith (2 parts, 2008)
• From Raxacoricofallapatorius with Love (co-written with Clayton Hickman, 2009)
• The Wedding of Sarah Jane Smith (2 parts, 2009)
• The Empty Planet (2 parts, 2010)
• Goodbye, Sarah Jane Smith (co-written with Clayton Hickman, 2 parts, 2010)