FOR its first— -ever season of regular repertory at Lincoln Center, the Joffrey Ballet opened last night at the State Theater with the first American production of John Cranko's grandly theatrical ''Romeo and Juliet.''

So many ''firsts'' imply some risks and the Joffrey won its gamble on every level. Americans initially saw the Cranko treatment of Shakespeare's play to Serge Prokofiev's score when the Stuttgart Ballet presented it here in 1969 with Richard Cragun and Marcia Haydee. Both of these dancers will, incidentally, recreate their roles as guest stars with the Joffrey on Saturday night.

What the Joffrey has been able to do is adopt the ballet as its own. Although Robert Joffrey proclaims a no-star policy for his own dancers, he has - as this New York company premiere proved - a highly appealing cast of juvenile leads.

Everyone in this production, down to Juliet's nurse and parents, is emphatically young. And this is not so startling as it is exciting. The characters are immature - they act on impulse with impetus. Any spark can ignite a catastrophe. And even the arbitrariness of the older characters seems explained by their lack of experience.

With their splendid technique, there is seemingly nothing that American dancers cannot dance. There are, however, some things that they cannot always feel. And so when the Joffrey first danced this ballet in Washington last December, the dancing certainly won out over the acting.

Now, this first of two different Joffrey casts has deepened its characterizations to a surprising degree. James Canfield's Romeo is magnificently danced at every moment. But he is also the production's most persuasive character. He gives us a Romeo all too ready for love, pursuing Deborah Dawn's fleeting Rosalind and literally immoblized by his first sight of Juliet.

As Juliet, Patricia Miller has transformed her previous blandness into something quite wonderful - a portrait of an extremely shy and childish young girl, as fearfully evasive of love as her Romeo seeks to embrace it. There are times when her beautifully placed dancing is more careful than passionate but her characterization is now a convincing complement to Romeo's brashness.

As Mercutio, Luis Perez shares most of the classical dancing and he has fully developed a mocking playful demeanor that is conveyed through the dancing. As for those who stalk through this costume drama, Jerel Hilding makes a superbly casual Tybalt - a smoothie of a villain who quietly appears to vent his rage for rage's sake. Tom Mossbrucker's Paris is as young as Juliet - and as easily offended. First prize for histrionics goes to Charlene Gehm's sexy Lady Capulet, who certainly know how to tear her hair and clothes apart when her more than favored kinsman, Tybalt, meets his timely death in Act II.

I once said Cranko's version was a production for the tired businessman and balletomane alike. Even the tired balletomane will now have something to gasp about. The Joffrey's rendering, supervised by Georgette Tsinguirides of the Stuttgart is lavish and formally fascinating.

Created in 1962, Cranko's treatment triumphs largely and simply because it gives a familiar story its own atmosphere. And that atmosphere is one of a small Italian town - Verona - whose smallness makes it impossible for feuding clans to avoid constant skirmishes that lead to tragedy.

Moreover, this is a town, like many in Europe even today, whose folk are still linked to the countryside. Anyone keen on rural fertility rituals will recognize Cranko's inspiration when his second act introduces a harvest festival, replete with masked figures. Cranko's peasants sell their produce in the market square and they hurl fruit at one another across the entire stage. But even such highly picturesque moments have a dramatic purpose. All of Verona - from peasant to lord - is caught up in the clan warfare between the Capulets and Montagues. The folk throw carrots and oranges. The aristocrats cross swords.

There is formidable unity to Cranko's dramatic conception here. The symmetry of Shakespeare's play finds its counterpart in the symmetry Cranko creates for the Montagues and Capulets. The two sides face each other in the first act, each line advancing toward the other - step by step.

The drama bursts out when Cranko shatters this symmetry. Law and order still reign as long as the Duke of Verona can appear flanked by the two clans. Yet after Tybalt has killed Mercutio, a stage filled with people suddenly seems emptied. Tybalt stands isolated at one end, solitary and menacing, waiting for Romeo. At the opposite corner, the same crowd has shrunk seemingly to a ball, clustered up front by Mercutio's body.

And so this is a highly pictorial version, a tapestry in which events interweave - where the private tragedy of two teen-age lovers is seen as part of larger public drama.

Many of Cranko's effects are highly formal, based on sophisticated spatial orderings. He is helped completely in this regard by the two- tiered set, brilliantly designed by Jurgen Rose. The decor, incidentally, is on loan from the Vienna Opera Ballet, and the production has received a crucial $300,000 grant from the Eleanor Naylor Dana Charitable Trust. Allan Lewis conducted.

photo of dance members