The 'Hitchcock' actress - who split from boyfriend Nate Taylor last month - only recently began dating the French journalist after being introduced by mutual friends.
Both Scarlett and Romain are close friends with French tattoo artist Fuzi, who earlier this month tattooed Scarlett with a horseshoe and the message 'Lucky You', on her rib cage.
One onlooker said, "They were very lovey-dovey and holding hands under the table all night. They were holding each other while outside smoking in the cold.
"He was dark-haired and slightly taller than her but skinny and he may have been speaking French at one point."Last month, Scarlett - who was once married to Ryan Reynolds - reportedly dumped advertising executive Nate just days after she was spotted "completely flirting" with one of Lindsay Lohan's close friends.
A source said, "They never officially lived together, but Nate has moved all of his stuff out and back into his apartment. The relationship is over. It has not been amicable."