Roukin was born in Southport and currently lives in northern New Jersey. He displayed an interest in drama from an early age. He completed secondary school at Merchant Taylors' School, Crosby where he was involved in many school productions. He goes back to the school to give acting workshops to pupils involved in drama and English. Roukin went on to train at the Bristol Old Vic Theatre School, graduating in 2003. Roukin finished filming Bright Star, directed by Jane Campion and based on the three-year romance between 19th century poet John Keats and Fanny Brawne.

Roukin starred in the 2008 film Happy-Go-Lucky as the love interest of the main character, Poppy (played by Sally Hawkins). Jonathan Romney's review of the film on the Independent website says of Poppy that "Realising one of her pupils is unhappy, she takes action that results in her meeting a simpatico social worker (Samuel Roukin), leading to possibly the single most convincing, no-nonsense, outright charming flirtation scene I've seen in cinema." The film, directed by Mike Leigh, won a host of nominations and awards worldwide.

Roukin also portrayed British Lieutenant-Colonel John Graves Simcoe, one of the main antagonists of the 2014 AMC series Turn: Washington's Spies, a period drama about American Revolutionary War spies.