Headers from Dean Lewington and Darren Potter, plus Stephen Gleeson's cool finish condemned Rovers to their third straight defeat on the road and left the Dons nine points adrift of the play-off places.
And Robinson said: "We all believe - we need six wins out of nine now.
"It's disappointing because it should be five out of nine as we all know Tuesday night against Shrewsbury we should have got more than we got out of the game.
"Arguably Ronnie Moore has been one of the managers of the year this year, this Tranmere side has been top for a lot of the season so that is a 3-0 win against a very good side.
"We've got a mountain to climb, but we've gone up a few metres. We've got a lot further to go and we're looking forward to the fight.
"It's frustrating because when this team is challenged and when we're playing against good teams we perform at better levels.
"I thought we were comfortable and I never really feared that the result would be anything other than us winning the game.
"Ourselves and Tranmere have probably got the two smallest squads in the league and it looked like that second half - they were two very tired teams."