Rooney's place has been called into question in recent weeks, but Lennon has said that the Manchester United forward is key to his country's chances in their World Cup opener against the 2006 winners.
"There's a big onus on Wayne Rooney tonight. He's a big-game player and that's what England are going to need," he told BBC Sport.
"There's been a lot of pressure on him, unjustifiably so, because he's a top player.
"I think it's going to be cautious game to start with but I think it will open up as the heat has an effect."
Rooney has never scored at a World Cup.