The actor, who played ADA Michael Cutter for three seasons on the flagship series, will reprise his role on an upcoming episode of Law & Order: SVU.
When Cutter returns in the Season 13 premiere, titled "Scorched Earth," he has been promoted at the DA's office and is overseeing the ADAs assigned to the Special Victims Unit.
"If Cutter was a bit of a hot head in the past, the passage of time and some added responsibility in his new job has made him more mature, and perhaps a bit more jaded," executive producer Warren Leight said.
Roache, 47, starred on the original Law & Order from 2008 to 2010 when the show was canceled in its 20th season. "I learned a lot from my time on Law and Order and it's going to be interesting to experiment with Cutter's development in this new context — I think Special Victims is going to be an area where Cutter's passion for justice can really come forth," Roache said.
Roache recently completed shooting on the upcoming ABC miniseries Titanic, airing in 2012.
The new season of Law & Order: SVU premieres on Wednesday, Sept. 21 at 10/9c on NBC.