"The first half was difficult," said the 44-year-old coach. "The opposition were well organised, they played lots of long balls and we hadn't really managed to make any clear chances. I asked the players to be patient and not get annoyed. There's nothing wrong with winning a game in the last ten minutes.
"The match opened up in the second half. Romania had chances as well, but it was in the last 15 minutes that we made a difference. The freshness of the team and the freshness of the substitutes made the difference."
Blanc introduced Remy, Gourcuff and debutant Dimitri Payet in the second half, and all three played a part in France's two goals. Remy finished crisply to break the deadlock in the 83rd minute and it was from Saint-Etienne striker Payet's pass that Gourcuff sealed victory in the third minute of injury time.
"The victory came from the bench," said Blanc, who is striving to restore confidence in his squad after Les Bleus' disastrous 2010 FIFA World Cup South Africa™ campaign. "You have to play matches with 14 players.
"In the second half we brought on players who can dribble and stretch the play. We brought on quick players to make chances and that's exactly what happened with Loic."
France now top Group D by a point from Belarus and Albania, ahead of a home game with Luxembourg on Tuesday. Blanc confirmed that he may rotate his side for the match in Metz, but warned that players and fans alike would have to be patient over the course of qualifying.
"We're creating something and it's bearing fruit," he said. "We need to re-invest this energy, because there will be difficult periods. But for the moment there's a lot of pleasure."
"The second period was much closer, with lots of chances at both ends. It's normal that France made more chances though, because their technical quality was incredible."
Defeat leaves Romania fifth in the pool, a point ahead of Luxembourg, and their next match does not arrive until they travel to Bosnia-Herzegovina on 26 March next year.