Rooney's place in the England line-up has been questioned with strike duo Harry Kane and Jamie Vardy in fine form ahead of Euro 2016.
But former Manchester United team-mate Ronaldo has no such queries, insisting the 30-year-old is a key for Roy Hodgson's side.
Ronaldo and Rooney have history at international level, with the Portuguese star getting the Englishman sent off during a clash at the 2006 World Cup.
"A match against England would be very emotive for me – because of Wayne Rooney and because of many other things too. Roo is now a leader and that’s not a surprise," the Real Madrid star told the Daily Mirror.
"I was always convinced that he would be a star for England and, inevitably, captain one day. It's a perfect role for him after the era of [David] Beckham and [John] Terry.
"For me, the character and pride of Rooney is unique – he's still very important for England."
While England face Russia, Wales and Slovakia in Group B, Ronaldo and Co. are set to meet Iceland, Austria and Hungary.
Ronaldo believes Hodgson's men are capable of challenging in France, particularly with Vardy and Kane coming off strong Premier League seasons.
Kane won the golden boot with 25 league goals, while Vardy struck 24 in Leicester City's title-winning campaign.
"I've watched some of England's recent matches and they have been good to watch. They could do well this time," Ronaldo said.
"For me, England always have a chance to do well in big tournaments and this time they are arriving in France with some interesting young players who have a big future.
"The connection in the team and the team spirit looks positive.
"Both Jamie Vardy and Harry Kane have scored a lot of goals and had success this year too."