The O's are now five points clear at the top of League One after extending their record-breaking start to the season to eight straight wins by beating Rosler's side 2-0 on Monday night.
Brentford are already 12 points behind their London rivals and Rosler admitted: "That's too much.
"If they can keep their players fit they will be in and around the play-offs. Last year Tranmere had a similar run and fell off the pace. I don't expect Leyton Orient to do that."