The 23-year-old had been airlifted to hospital in Lille after receiving CPR at the roadside following a crash during the 257-kilometre race.
The team added that the cyclist died "in the presence of his family members and loved ones, who we keep in our thoughts".
Alberto Contador, twice victor of the Tour de France, wrote on Twitter: "My heartfelt condolences to the family and friends of Michael Goolaerts, since the end of the race I have not stopped thinking about him". Swiss national road champion Silvan Dillier (Ag2r-La Mondiale), who was part of the day-long breakaway, was the only rider able to stay with Sagan as the kilometers ticked down.
Once the man who won the last three editions of the road cycling world championships jumped away from the group of main favourites with 55km left, he never looked back. He rode several of the cobbled classics and semiclassics this season.
It's just one of those races that takes a lot from you, not just physically but mentally too.
Paris: Peter Sagan (Bora-Hansgrohe) silenced the critics with a near-faultless and all-conquering performance to win Paris-Roubaix.
Paris-Roubaix is one of the five Monument classics along with Milan-San Remo, the Tour of Flanders, Liege-Bastogne-Liege and the Tour of Lombardy.
Unfortunately, 22-year-old Belgian cyclist Michael Goolaerts fell victim to these incredibly hard circumstances during this afternoon's race.
Record-setter Nadal roars back, Italy hold France
France will host the winners of the tie between Spain and Germany, from 14-16 September, for a place in the Davis Cup final. The French came out on top in a dramatic match earlier in the day when Lucas Pouille defeated Andreas Seppi in five sets.
Guardiola seeks flawless game against Liverpool
It's more than 90 minutes but we showed many times, in a short period we can create chances and you have to be clinical. I like to watch my team, the way we play this season and the way we played in the first half against United.
Sebastian Vettel wins the Bahrain Grand Prix
During a routine pit stop, Raikkonen's auto was released too early and hit one of the team's mechanics as he accelerated away. Raikkonen left the Ferrari pit box after being given a green light - but one of his tyres was not put on correctly.