Roux was born at Pembury maternity hospital in Kent, whilst his father Albert Roux was working for the horse race trainer Major Peter Cazalet. The family moved to London in 1967, when Albert and his brother Michel Roux opened Le Gavroche. Roux Jr. was subsequently educated at the private Emanuel School in Battersea, south-west London
After leaving school at age 16, Roux undertook apprenticeship work with Master Patissier, Hellegouarche in Paris. From summer 1979 until January 1980, he worked as a commis de cuisine at Le Gavroche, under both his father and his uncle. He then spent two years as a commis de cuisine trainee under Alain Chapel at his hotel and restaurant in Mionnay, in the Rhône-Alpes region near Lyon.
After undertaking basic training with the French Army, from February 1982 to March 1983 he served his military service at the Elysee Palace, working for both Presidents Valéry Giscard d'Estaing and François Mitterrand. Having finished his military service, Roux then worked for four months in Paris: two months at Charcuterie Gérard Mothu in St-Mandé; and then two months at Boucherie Lamartine on the Avenue Victor-Hugo.
Returning to London, in August 1983 he learned accountancy at Finlay Robertson, before becoming the Sous Chef at Gavvers. He then took the opportunity to work with renowned chef Pierre Koffman at his Chelsea restaurant La Tante Claire, reverting to the rank of Commis Chef to do so. From October to December 1983, he worked at the Mandarin Hotel, Hong Kong.
Having served his apprenticeship and training mainly away from the Roux brothers' British business empire, he joined his uncle at the Waterside Inn, in Bray, Berkshire in 1985, before working with his father at Le Gavroche from the April of the same year. He then worked in and managed the Roux brothers catering business for three years, before returning to Le Gavroche in 1990, the year the two brothers split their business down family lines. When his father retired in 1993, Michel Jr took over the world-famous restaurant.
A food consultant to the Walbrook club since 2003, he also consults for the fine dining providers Restaurant Associates. Roux has also written several books, including Le Gavroche Cookbook; The Marathon Chef; and Matching Food and Wine, which was named the best book on matching wine and food at the Gourmand World Cookbook Awards.
Roux has made various television appearances, including on his friend Gordon Ramsay's ITV produced Hell's Kitchen, and as an expert judge on the BBC Two programme MasterChef: The Professionals (2008–13). In 2012 he appeared as a guest judge on Masterchef South Africa. From 2013 until 2014, Roux co-presented BBC Two's Food and Drink alongside Kate Goodman. In 2013, he appeared as one of the mentors in the series The Chef's Protege.
In March 2014, Roux announced that he was leaving the BBC due to a conflict over his brand ambassadorship for Albert Bartlett Rooster potatoes. In 2015, Roux returned to television and presented First Class Chefs for the Disney Channel and Kitchen Impossible with Michel Roux Jr for Channel 4.
In November 2016, the Guardian reported that whilst Roux’s restaurant made over £250,000 pounds in profit in 2015, he was paying some of his chefs less than minimum wage. A chef showed the Guardian journalist Robert Booth evidence that chefs typically put in over 65 hours of labour per week, only earning about £5.50 per hour. Work days began at 7am ending at 11.30pm, with only one hour break between lunch and dinner times and sometimes as little as 15 minutes for meal times.
Booth's Guardian article noted that in response to the expose, "Roux said ... he was “embarrassed and sorry” after the Guardian revealed he was paying chefs as little as £5.50 per hour when they were working 68 hours per week."
In late 2016, it was revealed Roux was keeping servers tips and service charge. In light of this, he vowed to "scrap tips and service charge", instead including them in the cost of a meal. This has garnered backlash from customers and critics alike, as it leaves the customer with no viable way of choosing how much to tip, and encourages the inference that the optional service charge is now mandatory.
Roux is married to French-national Giselle, who has worked in the restaurant business for numerous years and is currently the secretary at Le Gavroche. The couple have a daughter, Emily, who is training to be a chef. The family lives in London.
A lover of alcohol, Roux does not drink between Monday and Friday, but enjoys Krug champagne at the weekend. Roux is a big rugby fan and is an honorary member of Harlequins and goes to most matches. He also likes Manchester United, and is a keen marathon runner, having run the London marathon twelve times to raise funds for the children's charity VICTA (Visually Impaired Children Taking Action). Michel's interest in this charity stems partly from his own experiences with vision loss due to retinal detachment in 2004 and 2007 (one in each eye) and cataracts in 2008 and 2010 (again, one in each eye). Subsequent medical treatments led to improvements in vision.