Sebastian was born in Paris to a French father and Scottish mother. As a teenager, he lived for six years on a sailboat with his parents and brothers, Guillaume and Fabien, travelling to the Mediterranean, Africa, South America, and the Caribbean. Roché is mulitlingual – able to speak English, French, Spanish and Italian fluently.
After graduating from the prestigious French National Academy of Dramatic Arts, Roché moved to the United States in 1992.
Sebastian is known for his role as Mikael Mikaelson in both The Vampire Diaries and The Originals. He also portrayed Kurt Mendel on Odyssey 5, Jerry Jacks on General Hospital, Thomas Jerome Newton on Fringe and Reichsminister Martin Heusmann on The Man in the High Castle.
In 2016, Sebastian co-starred as Cardinal Michel Marivaux in Paolo Sorrentino's drama series The Young Pope, alongside Jude Law and James Cromwell.
Sebastian was married to Vera Farmiga for seven years until their divorce in 2004. Sebastian has been married to Australian actress Alicia Hannah since 2014. He currently lives in Los Angeles, California.
- Sebastian is said to deeply respect Misha Collins for what he does and openly considers Misha to be his "brother in spirit".