The 24-year-old Texan, who won the world title in 1993, has been looking for a new team since Motorola announced they were retiring from cycling at the end of the current season.
In the team coached by France's Cyrille Guimard -- the man who launched the careers of Bernard Hinault and Greg LeMond -- Armstrong will be supported by a strong French squad.
Christophe Capelle and Francis Moreau, both team pursuit Olympic champions, Laurent Jalabert's younger brother Nicolas and Tour de France stage winner Cyril Saugrain will be among Armstrong's team mates next season.
Boardman, who broke the world 4-km pursuit record at the world championships last week, plans to attack the record of Swiss Toni Rominger of 55.291 km, set in Bordeaux in October 1994, on the Manchester indoor velodrome, probably on Friday.
The Briton hurtled twice round the 26-km course in Brussels at an average speed of 51.25 kph, finishing one minute 37 seconds clear of American Lance Armstrong with Belgian Johan Museeuw, last year's winner, another 12 seconds adrift in third place.
Museeuw started fastest, leading Boardman by three seconds after four kilometres.
But Boardman, the winner here in 1993, then moved up a gear and was five seconds faster after 13 kms before taking full control.
Tour de France winner Bjarne Riis of Denmark suffered the indignity of being overtaken by Museeuw after 37 kms although the Belgian had started two minutes behind him.
Riis finished in ninth place, four minutes eight seconds behind Boardman.
Merckx's son Axel took 11th place, more than five minutes behind.
On the final day of the five-day championships, Rousseau defeated 1994 sprint champion Marty Nothstein of the United States 2-0 in the best-of-three final.
The Frenchman said: ``I didn't expect to win. The last time I beat Nothstein was two years ago at the Bercy track in Paris.''
The American appeared to be drained by a three-race battle to overcome the defending champion Darryn Hill of Australia in the semifinals.
Hll crossed the line first in two matches but was relegated to second place for rough riding in the last 200 metres.
``I think I got robbed, I always seem to get bad decisions against Marty. I'll be out to beat him in next year's worlds on my home track in Perth,'' he said.
After losing the final Nothstein said: ``I felt good thanks to my win in the keirin earlier in the series, but today I could not find my power. The motor was not there I was riding on pure heart and determination.''
Marion Clignet completed a double for France, beating Lucy Tyler-Sharman of Australia in the women's individual pursuit final.
Clignet, Tyler-Sharman and third-placed Antonella Bellutti all broke the world 3,000 metres record during the event.
Clignet has adopted the streamlined ``Superman'' riding style, developed last year by Britain's ex-world champion Graeme Obree.
``It made an amazing difference, as much as four or five seconds, I got more power and did not move about so much on my bike,'' Clignet said.
A countback was needed to decide the 40-kms points race title, won by Rossello Llaneras of Spain from Michael Sandstod of Denmark.
Llaneras and Sandstod lapped the field with an early attack, and spent the rest of the race battling for sprint points. Neither rider succeeded in gaining an advantage and they finished level on 29 points.
Llaneras was awarded the gold medal, becoming the first Spanish winner of the title, thanks to scoring more lap wins than Sandstod.
Defending champion Silvio Martinello of Italy missed the breakaway and had to settle for the bronze medal, one lap in arrears, despite having the highest points score.
France, winners of this year's grand prix-style World Cup competition, confirmed their status as the world's most successful track nation, winning four of the 12 championships here.
Italy and Australia took two each, with the rest going to Britain, Russia, Spain and the United States.