The jury, seated beside a chart of mugshots connecting the alleged cocaine kingpin to a network of drug-slingers, found Rosemond, known as "Jimmy Henchman," guilty after a day of deliberation.
"I'm obviously very disappointed," Rosemond's attorney Gerald L. Shargel told TheWrap.
Shargel told the court his client was never involved in the cocaine trade.
"I stand by what I said in court," he said, adding that his client plans to appeal before the sentencing, the options for which include life in prison.
Rosemond is perhaps more notorious in the hip-hop community for his alleged involvement - which he has consistently denied - in the bicoastal feud that led to the murders of rappers Tupac Shakur and Christopher Wallace, known as Biggie Smalls.
He served as the CEO of Czar Entertainment which managed big-name artists including the Game, 50 Cent, Akon, Brandy and boxer Mike Tyson.
Prosecutors accused Rosemond of operating a cross-country cocaine ring that shipped the drug to New York and sent the money to the West Coast, according to court documents obtained by TheWrap.
The U.S. attorney's office in the Eastern District of New York could not be reached for immediate comment.