The duo has secured the Be at One site in Gresham Street where they plan to open a French restaurant serving wines from around the world.
The two-storey site is expected to open this summer.
Last week, former Le Manoir aux Quat'Saisons head sommelier Rousset, told BigHospitality he would consider opening more restaurants following the launch of his first solo project.
Blandford Comptoir, a relaxed Mediterranean restaurant serving 250 different wines, will open in Marylebone next month.
"I would like to expand the Comptoir format, but if I did it open more sites it would not be the same as this one," Rousset said. "I don't want it to be a copy and paste concept, but it would have similarities. There would always be a focus on wine."
Between them Rousset and Devaney, both Master Sommeliers, have worked in a host of Michelin-starred restaurants. Devaney, who was named Sommelier of the Year in 2008, started as an apprentice at The Capital Hotel in London before working in France for Pierre Gagnaire and then at Tom Aikens' eponymous restaurant.
After leaving Le Manoir, Rousset set up Texture and 28-50 Restaurant Group with chef Agnar Sverrisson, but he left the business last year to pursue his own projects.
Matthew Englender, surveyor at Restaurant Property, who helped secure the site for the pair, said: “Xavier Rousset and Gearoid Devaney are extremely talented master sommeliers so I am delighted to have helped secure a site for them within the heart of the city."