The 35-year-old Rose wore a suit and tie when he appeared before a federal judge in Nashville, saying nothing but "yes, sir" when asked if he understood the charges and his plea.
The Drug Enforcement Administration said Rose's arrest was part of a larger investigation into a major GBL trafficking organization. Rose surrendered to authorities shortly before he entered his guilty plea.
The indictment said Rose admitted he received GBL from a person in Tennessee while a member of the Chattanooga Lookouts, the Double-A affiliate of the Cincinnati Reds.
He also said he supplied half the players on that team with the drug. Rose said his teammates would take GBL to "wind down" after games, DEA spokesman Rusty Payne said.
Under a deal with prosecutors, Rose could be sentenced to 21 to 27 months in federal prison and fined up to $1 million.
GBL, or gamma butyrolactone, is sold under the counter at retailers and gyms with claims to build muscle, improve physical performance, enhance sex, reduce stress and induce sleep. When taken orally, GBL is converted to the "date-rape" drug GHB, or gamma hydroxybutyrate.
Lookouts assistant general manager John Maedel said Monday the team was aware of the story. "We don't know anything about it and can't comment," he said.
Maedel said Rose was on the Chattanooga roster in 1997, 2001 and 2002.