The Manchester United striker has fallen under increasing scrutiny in the build-up to the tournament, with former team-mate Phil Neville describing debate over his fitness as a "witch-hunt".
The 28-year-old’s place in Roy Hodgson’s team has been questioned, with youngsters Raheem Sterling, Adam Lallana and Ross Barkley all pushing for places among the forwards.
But, addressing the media in Rio de Janeiro three days before England’s Group D opener against Italy, Rooney hit back at his critics.
“I don’t care about what anyone says. I’m ready for this World Cup. I’m focused and I feel I’ve still got a massive role to play in this team," he said.
“Of course there is competition for places, there always is playing for your country, but I’m ready for that and I’m not worried about anything. There is so much ability and it’s a joy to be a part of.
“I feel great. I feel 100% fit and ready for the tournament. I’m not going to sit here and say ‘expect this, expect that’ from me, I know how these tournaments work, but I will give my best for the team.”
Rooney confirmed that Danny Welbeck will be available for the Italy clash despite sitting out training with a thigh issue on Wednesday, and Hodgson’s wealth of attacking options has led to some debate over who should play.
But Rooney insists: “It’s exciting. The younger players are bringing energy into the team and it’s great to be a part of.
“This is the best squad of players I’ve been involved in since I’ve been with England. I’m looking forward to the tournament and the future – it looks bright.
“Success and trophies are always what have motivated me at club and at England level. To win a trophy with England would be the greatest thing possible.”
England were knocked out by Italy in the quarter-finals of Euro 2012 but Rooney believes this influx of youth means they are a different side that has now surpassed this weekend's opponents.
“I think we’ve moved ahead of Italy. Not just the team, but the squad we’ve got is youthful, with a lot of energy, whereas Italy more or less have the same squad,” the United forward explained.
“It will be an interesting game to see how we’ve moved on and progressed over the two years. We’ve prepared well. We are ready for the game and looking forward to it."