Roma sign Vainqueur from Dynamo Moscow
Vainqueur is the second Frenchman in a week to join the Rome club after defender Lucas Digne signed on loan from Paris Saint Germain.
Roma did not release any financial details of the deal or the length of Vainqueur's contract.
The 26-year-old midfielder told the official Roma website: "I'm here because Roma are a great team and Rome is a wonderful city. I'll give my all for this very famous shirt."
Vainqueur came through the youth ranks at Nantes and made 90 appearances for the Canaries over five seasons before moving on to Standard Liege in 2011.
He signed for Dynamo Moscow last summer and went on to score twice in 27 games for the Russian Premier League outfit.