Last weekend, though, as competitors formed up for this year's race, Roubaix's image for tough but honest sporting endeavour was eclipsed by a quite different and far less inspiring image.
Three weeks before, the city hit the headlines with a chain of events that began with a car bomb outside police headquarters and ended with a chase, shoot-out and hostage-taking in Belgium.
In between, there had been a siege and gunfight in the city's grim backstreets in which four men were killed, two policemen injured and a house gutted. Automatic weapons and grenades, along with fundamentalist Islamic literature, were found in the ruins.
To Roubaix's detractors, who already regarded it as the distillation of almost every French ill - industrial decline, unemployment, immigrant ghettos, the spread of Islamic fundamentalism, drug trafficking, violence - here was proof.
But the first response from the authorities was soothing, along the lines of: "Just a spot of gangsterism; it's all over now."
The second response evinced anxiety verging on panic: links between this violence and Islamic fundamentalist terrorism could not entirely be ruled out, said Jean-Louis Debre, the Interior Minister. After years of neglect, Roubaix had become a national concern.
The usual approach to Roubaix from Paris is by the recently completed tramway from Lille. From there, it is hard to believe everything that is said about the town: there are landscaped parks, broad green verges and large houses, reminiscent of solid Victorian suburbs in Britain.
However, as the tram reaches its terminus, two minutes' walk from Roubaix's central square and town hall, it is evident all is far from well. It has the look of every unhappy French city.
There is a profusion of graffiti and litter; listless gatherings of poorly dressed young people, many of them brown, fewer black and white; streets of boarded-up shops; elderly people scuttling along the inside edge of the pavement with modest bags of shopping.
There is abundant evidence of regeneration efforts, most for the short term and done on the cheap: gaudy metal frames and buildings set at jaunty angles, incompatible with what survives from the past. What does survive from the past is dirty and neglected. The liveliness and tasteful restraint of "happy" French towns is absent.
In the tiny heart of the city, the broad square and official buildings with their tall, dark and narrow facades, have something of old-style Belgium.
The rest is a mish-mash of grid streets lined with old terraced houses, a couple of new-ish hotels - with high metal fences around them - and patches of recent, high-density housing in what are only theoretically pedestrianised areas.
In its heyday, Roubaix was known as the "city of a hundred chimneys" and was the hub of the French textile industry. Over the past 30 years, it has almost vanished.
Few jobs have arrived to take the place of the thousands lost. Immigrants who arrived to work in the mills - some directly from France's colonies, others from Belgium - found themselves and their families without work or the prospect of work.
None of this by itself explains why Roubaix should over the past year or so have come to combine some of the most violent crime in France - with the acknowledged spread of fundamentalist Islam among a younger generation born and educated for the most part entirely in France.
One theory is scotched at the outset by everyone you ask in Roubaix. It is not, as Philippe Aziz, author of a recent book states, a city with a non-French majority - however non-French is defined.
More than a third of its population may be of immigrant origin, but everyone stresses that it is not - as Mr Aziz claims - France's first "Muslim" city.
In some districts, though, people "of foreign origin" are in a big majority.
One city official said that this was a "mistake", the result of both negligence and benevolence. "We wouldn't want to assist that sort of concentration today but how can you undo it?" he said.
He also felt the state might keep a closer watch on the mosques, even reduce their number and work with the more moderate clergy: "But there we have a problem: where Islam is concerned, the separation of church and state in France can be a liability."
In the backstreets of the Alma-Gare quarter, near the scene of the recent gunfight, you can see adolescent boys flaunting Arafat-style headgear; bareheaded girls are few and mostly of identifiably Turkish, not North African origin. There are mosques, big and small, and - it is said - very many more in cellars and converted backrooms of houses. Islam has claimed even thoroughly French converts: two of those killed in the recent shoot- out were of French origin, a fact that leaves officials and others struggling to find explanations.
Even so, the police and officials of the centre-right council in Roubaix are reluctant to accept the existence of any link between "racketeering", largely drugs-related crime, and Islamic terrorism.
The drug problem is manifest and blamed on the proximity of the Belgian border (which runs through the edge of Roubaix), the liberal drugs laws in the Netherlands and unemployment. Roubaix's south-eastern suburb of Hem is admitted by all to be saturated with drugs.
The appeal of Islamic fundamentalism for disillusioned young people of immigrant parents is also conceded.
There were arrests in Roubaix, as there were in many large French cities, after the summer bout of Islamic terrorism in Paris and Lyons.
Islam supplies a purpose, a faith and an identity to second- and third- generation North Africans who feel let down by the French system.
In Roubaix, these young people are largely French citizens but they complain that they were never treated as "properly" French, never given an equal chance. Their parents' hopes, they say, were betrayed.
While the possibility of links between young Muslims in search of a purpose and criminal violence is something officials - locally and nationally -would prefer to minimise, local people and reporters take it almost for granted.
"Of course, many start off as idealists; they embrace Islam in an attempt to flee drugs and violence," a local reporter told me, "but they are used by others, including some Muslim clerics. They need funds for their `holy war' and all means to acquire them are good."
According to this theory, the link between organised crime and Islam, if not already proved, is only a matter of time.