Rolland dismissed Warburton after 17 minutes for his tackle on French winger Vincent Clerc.
The decision was met with disapproval by many spectators, but O'Brien was firm in his assessment that the outcome was correct.
"Alain Rolland's decision to issue a red card was absolutely correct in law and in keeping with the clear instructions that match officials have received in recent years regarding dangerous tackling," he said.
"Alain is a highly experienced referee and had a clear view of the incident, which enabled him to make an accurate and instant decision.
"Player welfare is paramount and unions, teams and match officials are all aware of the responsibility to eradicate dangerous play. This message was reiterated as recently as the week before Rugby World Cup 2011 kicked off, when we hosted briefings at a workshop with match officials and coaches."
Warburton has since been handed a three-week ban for the incident. Wales will not appeal the decision.