Lille title hopes revived as Roux sinks Sochaux
Striker Roux, who joined from Stade Brest last month, headed home from a corner-kick to give the visitors a deserved victory.
The win put Lille on 45 points from 24 games, six points behind leaders Paris Saint-Germain, who were held to a 2-2 draw at Montpellier on Sunday.
Elsewhere, Saint-Etienne jumped up to fourth on 42 points after a Pierre-Emerick Aubameyang hat-trick earned them a 4-2 home victory against Lorient.
Lorient went ahead four minutes into the second half courtesy of a Arnold Mvuemba penalty four minutes into the second half before Gabon striker Aubameyang proved unstoppable.
He struck in the 56th and 68th minutes, only for Mathias Autret to equalise in the 76th.
Midfielder Bakary Sako, however, found the back of the net with two minutes left and Aubameyang wrapped it up in the last minute.