When the Royal Ballet announced that it was going to perform Jewels, a three-act ballet that showcases a bevy of ballerinas by assigning them to certain precious gems, there was a game you could play. Which Covent Garden lovely would be cast in which part? Emeralds is the old-fashioned romantic one, Rubies embodies the sexy modern extrovert and Diamonds is a homage to the classical princess. It wasn’t hard to pick and choose the winners in each, but one dancer defied speculation. She was Tamara Rojo and the reason you couldn’t pigeonhole her is that she is all three jewels in one.

Ever since she joined the Royal Ballet seven years ago this Spanish beauty has been steadily proving that she can represent every aspect of womanhood on stage, be it the lustrous innocence of Aurora, the strange wildness of Odette, the scary madness of Giselle or the frenzied passion of Juliet and Manon. It’s not every dancer who can travel the repertoire with such ease or slip on so many different dramatic colours.

And so we come back to Jewels. George Balanchine’s 1967 trio of plotless ballets offers an unparalleled chance to savour Covent Garden’s ballerinas, with five of them on show in a single performance. You expect the lead in Diamonds to get all the glory and the two women in Rubies to have all the fun. But Emeralds, with its gracious restraint and 1840s comportment, is the hard one because the glitter is modest, the sheen deliciously old-fashioned. It’s the one that catches audiences by surprise.

And that’s where Rojo comes in. When she first heard that Balanchine’s ballet was coming, she consulted her inner jewel and came up Ruby. Not surprising, since Rubies, with its witty acrobatics and snazzy streetwise accents, would seem tailor-made for Rojo’s technical brilliance and animated personality. Yet, as her Giselle has shown, when it comes to looking like a 19th-century lithograph, no one beats Rojo.

“When I first heard about Jewels, I wanted to do Rubies because I do have a certain amount of technique and I enjoy showing it off,” Rojo says. Her English is impeccable, yet another reason for those who meet her to be impressed. “I knew Rubies would give me a bigger chance to show off, but actually I’m enjoying learning Emeralds. It’s good to be reminded of what Romanticism really looked like, its femininity and delicate use of the upper body. And how every pose must be held just so.”

At this point she morphs into one of those iconic Emeralds images, head demurely down, her dark expressive eyes peeking out of lush eye-lashes, her wrists softly suspended in dainty anticipation. For Rojo the challenge is to “recreate an old-fashioned style without looking old”.

That famous technique of hers, so splendidly strong and etched with a sexy confidence, is what usually impresses first, the way she detonates pirouettes and delights in luxurious long balances, and can’t help dancing everyone else off the stage. “It’s the result of a lot of hard work every day, and of stubbornness. That’s my secret: I never let go until it’s perfect. I enjoy the challenge; I’m the person who wants to run one second faster. My coach, Loipa Araujo, says the only way to stop me rehearsing is to hit me over the head with a hammer.”

Now 32, Rojo is at her peak, capable of exquisite refinement and outrageous daring, of voluptuous sensuality and mercurial temper. “I believe an artist should be the channel for all those things. I want to know what each choreographer has to tell me; the way to do that is to embrace the style of each ballet we do rather than adapting it to what suits me.”

Life at the Royal is giving her plenty of opportunity to adapt. She opened this season as Nikiya in La Bayadère, a ballet that played to her fondness for sublime otherwordly spirits. Next week she embodies the polar opposite when she dances a hot-blooded Juliet to Carlos Acosta’s Romeo. Significantly, their pairing in Kenneth MacMillan’s ballet is being filmed for BBC Television.

“Juliet changes every time I dance her,” Rojo says. “The first time I was naive and I truly believed in true love and never analysed what she did. As you grow up you realise that things are not black and white and you start overanalysing. Then you have to take that away and find a balance. The last time, for personal reasons, I found Act I hard, that joy of love, that total giving of yourself. This time I’m happier and I’m going to enjoy that far more.”

She dances almost everything in the repertoire and admits that her career is like a fairytale come true. As a young ballet student growing up in Spain she dreamt of coming to the Royal Opera House but never actually believed she would wind up in its plush surroundings. “It’s not like we have any choices in Spain,” she says. “We all know that ballet in Spain is nonexistent these days; there is nothing there, no jobs. From an early age as a dancer in Spain you know that you will have to leave.

“When I was a student I saw Manon on video and thought it was the most beautiful thing I had seen. I knew then that this was a role I wanted to dance. Romeo and Juliet too, and Mayerling: these were the ballets that touched me. It was my top dream to dance them, but I never believed it would happen.”

First came English National Ballet in 1997, where she was groomed as Derek Deane’s star attraction. Three years later she jumped ship to the Royal Ballet. All it took was a phone call to Anthony Dowell, the director at the time, and the nerve to ask him for a job.

She’s still loyal to the Royal but more and more she pursues guesting opportunities abroad. In June she will star in Deane’s Strictly Gershwin for ENB at the Albert Hall. If she could have anything she wanted at the Royal it would be a new Don Quixote (she’s the perfect Kitri), but she’s looking forward to the return of Mats Ek’s Carmen next season.

Rojo still has many happy years left as a dancer but, like the smart cookie she is, she’s also planning ahead. She hopes to direct a ballet company in Spain some day. The Government there, aware that Spain is training people to work abroad, has asked for her input on starting a new ballet company in collaboration with the University of King Juan Carlos in Madrid, where she did a degree in dance (a doctorate is next). Already she talks like a director, about foundations and budgets and the importance of financial accountability. “I listen, I analyse what other directors do and try to learn from them. I am still ambitious as a dancer and I certainly don’t want my career to finish early, but I also realise that the next step is not something to be fearful of.”

Jewels opens at the Royal Opera House (020-7304 4000) on Nov 23. Rojo dances Juliet on Nov 7, 12 and 16

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