The Daily Telegraph is reporting that under NRL regulations, Nikorima faces a 12-week ban.
Nikorima is set to appeal the finding though, with claims he has evidence that will clear his name.
There had been reports in the past few weeks that the Roosters had been looking to offload Nikorima to clear cap space for the signing of Cooper Cronk.
Carter pleaded guilty to supplying cocaine at a Sydney nightclub to ex-teammate Kenny-Dowall in court last month, with the matter adjourned for sentencing on November 29.
The Roosters and the NRL have refused to comment under the strict NRL and ASADA protocol.