Kean did not like the way his side were playing in the first half despite going a goal up via a Jason Roberts penalty.
Then David Mooney scored for the visitors on the hour mark and that seemed to wake Rovers up and they soon raced to a 3-1 lead when Ruben Rochina and summer signing Simon Vukcevic scored in quick succession.
And although Dean Cox grabbed a late goal back, Rovers managed to hold on for an important win.
"I thought we made hard going of it and I wasn't too pleased with how we played the first half," said Kean.
"We were a bit slow with our passing, there were too many backwards and square and when Orient had it we didn't show enough intensity to get it back so I thought we were poor.
"But reflecting on the whole game, when they came back into it we should have been four or five goals in front.
"But for poor finishing and a good goalkeeping performance I think the game would have been out of sight.
"I felt we had the possession but we didn't get it out wide."