His upbringing, on a council estate in Hong Kong, was a world away from his life today. Before he moved to London, aged just 17, to train as a psychiatric nurse — until discovering "you could make a living out of design" — he shared a two-bedroom flat with his seven siblings, parents and his grandmother, a dressmaker.
Now Rocha, 58, divides his time between homes in London, Dublin and the South of France and today he's showing me around the recently completed one-bedroom apartment in Dover Street, off Piccadilly, that he shares with Odette, his "lovely" Irish business partner and wife of 28 years.
When the couple are away from the capital, the W1 duplex — which sits above Rocha's eponymous three-storey lifestyle boutique — "comes in handy" for his son and two daughters, one of whom has followed in her father's footsteps to set up the flourishing Simone Rocha label.
Sitting in the L-shaped living room, he cuts a distinctive figure in a black linen suit, his trademark long hair draped over a crisp white shirt.
"This building was originally a pub," he says. "As soon as it came on the market, I knew it was perfect. It was built after the Great Fire of London so is about 400 years old, but it was so run down that we had to demolish the interior, even gutting the basement. We just kept the façade."
"I wanted to pull all the things I do together," he explains. "The same design principles run through all areas of my work. The common link is the use of natural materials, simple shapes and a calming effect."
And calm it is. A Zen-like quality running through each space makes it hard to believe we're in central London. Rocha worked closely on the flat with an architect from his Dublin headquarters.
"I love coming up with the ideas but my architect handles the practical side of things, making sure that the building doesn't collapse," he says. His favourite space is the open-plan living and dining area, which leads to a narrow galley kitchen and balcony. The building is on a corner and the living room has restored Georgian windows on two sides.
Rocha relaxes in the comfort of one of a pair of fabulous beaded African chairs he stumbled across in a New York flea market. He is a die-hard fan of markets — including London's Portobello, Paris's Porte de Vanves and the "wonderful" Cours Saleya that pops up in Nice every Monday: hence the joyful jumble of items that give this apartment its spirit.
Beaded boxes, bones and hand-carved wooden masks are decorative discoveries from Nairobi. And a 6ft-tall bird sculpture that greets visitors on the stairs is from Les Puces market in Paris. Paul Smith's shop on Albemarle Street, Mayfair, is also a source of vintage pieces, including the Fifties dining chairs.
Rocha is an avid collector of contemporary art. On the coffee table are wacky wire rabbit sculptures by Benedetta Mori Ubaldini, while Hella Jongerius's glazed plaster pots brighten up a side table. And The End, a sculpture of two Chinese girls by "cool" young artist Xiang Jing, is super funky.
"Though my interiors come from different parts of the world and from different periods, when they get together they become interesting. I don't like everything ultra-modern," he says.
It is fitting that he has designed a number of the furnishings himself, such as a black lacquered coffee table, linen-covered sofa, the 10-seater glass dining table and green glass console tables. Upstairs, he has made the walnut beds and hand-painted velvet bed throws.
The bold objects and bright fabrics contradict the deliberately plain backdrop. "I have stuck to a simple stone bathroom — sometimes less is more — and used clean, white walls and American walnut flooring throughout the property," explains Rocha. "White reflects the light and is a great backdrop for art. If you have a plain background, it makes the pieces more exciting. It is like fashion — if you mix too many strong colours you tend to take away from the personality."
And personality always comes before looks for this designer. "Whether it is a dress or a piece of furniture, there is no point in buying something because you think it is fashionable. A home should be comfortable and filled with things you love rather than what other people might enjoy looking at," he insists.
The same applies to location. Rocha, who once rented in Stoke Newington — "when it was cheap and not trendy" — and Swiss Cottage, chose to buy in Dover Street because it is surrounded by some of his most treasured haunts.
"Very often people have a wonderful home in a location that they think is cool but that they are quite alien to. In an ideal world, home should be close to the shops, galleries and parks you love to visit."
For Rocha that is The Arts Club, La Petite Maison, Scott's or Automat restaurants when he fancies an upmarket food fix. And the family-owned Le Petit Café, an "amazing value sandwich bar that has people queuing up at lunchtime" next door to his flat. On Saturdays you might find him in Pall Mall's fly fishing shop Farlows (he is a keen angler), strolling around St James's Park or watching a film at the Curzon Mayfair. "There is so much variety here, no matter what your budget."
With a wealth of successful business ventures under his belt, I can only assume that the self-made entrepreneur has a generous budget, but he insists that if he wasn't as privileged it wouldn't really matter. He would be perfectly happy to downgrade and spend most of his time relaxing with his family or fishing with friends. And you know what? I believe him.
Residing in a handsome flat in one of the most desirable areas in the world, Rocha is refreshingly humble and acutely aware of how both halves live. His is a real-life rags-to-riches story — and it couldn't have happened to a nicer man.
GET THE LOOK: give your home an instant John Rocha fix
* Yoruba large beaded chair (£950 at fromthetribe.com)
* Cornell walnut dining chairs (£169 a pair at made.com)
* Torbsy glass dining table (£160 at ikea.com) John Rocha red reactive floorstanding vase (£60) and matching half-moon vase (£14.40), both at debenhams.com
* Benedetta Mori Ubaldini bird and cloud decorations (£134-£169 at madeindesign.co.uk)
* Wire art elephant, handmade in Africa (£21.07, by Stribal at etsy.com)
* Dark wooden butterfly pyramid drawer (£29.99 at siiren.co.uk)
* Beaded trinket boxes (£5 at monsoon.co.uk) or £8 for a set of three at kilakitu.co.uk
* Sese wood "Fanti Mask" sculpture from Ghana (£43.47 at overstock.com)