FOR 13 years, the Crossroads Theatre presented its productions on a stage that featured a floor-to-ceiling Y-beam right in the center of the playing area. Today, their 14th season has been inaugurated in a new $4 million thrust-stage theater, ready to carry on the pioneering work begun in a converted New Brunswick, N. J. garment factory in 1978."I was driven by how few positive black roles there were for actors," recalls Ricardo Khan, who pulled together the fledgling troupe, along with fellow Rutgers graduate Ken Richardson. Using government funds, and support from New Brunswick's George Street Playhouse, they began producing black-oriented plays, with audiences numbering in the mid-teens. Today, Crossroads boasts more than two dozen premieres, Equity regional theater status, and a place at the forefront of African-American theater companies. After a dedication ceremony in the lobby of their new building, Mr. Khan says that the "one purpose we have is to create a new type of audience." To gain that audience, and to foster public interest in black culture and art, the company has developed an array of plays, many of which have moved on to other productions, such as Leslie Lee's "Black Eagles," and George C. Wolfe's "Spunk," an adaptation of three works by Zora Neale Hurston. The long-running off-Broadway musical "Further Mo by Vernel Bagneris started at Crossroads, along with Wolfe's "The Colored Museum," which toured nationally, traveled to London, and was broadcast on PBS's American Playhouse. In an era when regional theaters face lean financial outlooks, Crossroads benefits from a strong subscription base. Susan Settles, the audience development director, explains that the company has doubled its subscriptions in one year to more than 3,300. "Our goal is 5,000, and we're now getting responses from people in New York and Philadelphia, since our theater is just a little more than an hour away from both." Kicking off the new space is "Black Orpheus," a musical adaptation of the Greek fable by playwright OyamO, who moves the story to modern-day Trinidad. Approached by Khan to write something based on the Brazilian film of the same title, OyamO chose to integrate parts of the myth with Caribbean folklore to create a tropical scene of lush foliage, ruffled costumes, and exuberant dancing. The musical runs through Jan. 5. The 264-seat theater features the latest lighting, sound, and scenery equipment, and anchors a new cultural center in the town. Upstairs, the company's business offices share the building with meeting rooms, rehearsal areas, and practice studios. To maintain the family atmosphere that grew up in the converted factory, performers have to pass through administrative areas to get backstage. Actors, stagehands, secretaries, and business managers mix freely, giving everyone a sense of connection to the operat ion. "We've had to keep focusing on what's important," Khan says, noting that the growth comes at a perilous time for the arts. Even with corporate support and government funding, Khan recognizes the importance of audience commitment. Five benefit performances by Bill Cosby helped to raise funds. The touring NewROADS program resulted in increased subscriber response, and helped to make Crossroads the largest African-American theater company. "This is not a marketplace," Khan emphasizes, "it's a laboratory," s tressing the company's mission to expand opportunities for new works, voices, and expressions of African-American life through the arts. A painting by Leroy Campbell hanging in the new lobby depicts an audience watching a performance in the old theater staged around a massive gray Y-beam. "That beam taught us our most important lesson," Khan laughs. "We learned that, if you want to achieve your goal, sometimes you have to work around an obstacle. And you know what? We did."