"Roseland," now at the Avalon 1, stumbles right into the traditional pitfalls of so-called omnibus or anthology features, in which strong episodes tend to be obscured or diminished by the weak ones.

That's exactly what happens in this three-part romantic melodrama built around characters who frequent Roseland, the Manhattan mecca for ballroom dancers. A potentially stirring and memorable story about a young gigolo, admirably played by Christopher Walken, is sandwiched between two moldy items about aging women struggling to sustain romantic illusions on the Roseland dance floor.

The centerpiece in "Roseland" has such interesting dramatic possibilities that you can't help wondering why no one had the wit to expand it into a feature.

Did the filmmakers wreck their chance of developing a good movie plot out of the assumption that audiences would be more inclined to enjoy the enfeebled notes of pathos in the superfluous side panel stories.? Or did these notes grow out of their own misconceptions about what constitutes sensitive, soulful, compassionate storytelling?

"Roseland" is the sixth movie made by the team of producer Ismail Merchant, director James Ivory and writer Ruth Prawer Jhabvala. The earlier collaborations - "The Householder," Shakespeare Wallah," Autobiography of a Princess," "The Guru" and "Bombay Talkie" - were set in India and sustained a remarkably consistent quality of uninspired respectability. Merchant is the only Indian in the trio. Ivory is an American, attracted to India partly out of respect for the films of Satyajit Ray, while Mrs. Jhabvala is a German of Polish Jewish extraction whose husband is dean of architecture at Delhi University.

The introductory story in "Roseland" doesn't even qualify as an appealing annecdote. It suggests the sort of whimsy that might have been rejected years ago by the producers of "The Twilight Zone." A widow played by Teresa Wright sees herself as a dancing maiden whenever she passes a certain mirror in the arms or another Roseland regular, Lou Jacobi. Although she considers her partner a bit coarse, she begins nagging him to dance in order to trigger her youthful mirror vision.

This relationship is resolved when Jacobi pleads, "Can't you see I'm a person too?" Wright's eyes are opened, and the ceaseless, obtrusive narration, spoken by Helen Gallagher as a dance instructor who becomes a principal character in the second story, gushes over the prospect of partnership in more ways than one. Obviously, the next episode enters handicapped, andit's a miracle that it gets the movie up on its feet at all.

The gigolo portrayed by Walken has unexpected emotional depths. Desired by three different women - Joan Copeland as the effusive middle-aged divorcee who supports him, Gallagher as his former dancing partner and Geraldine Chaplin as a young acquaintance of his patroness - the hero is forced to choose between conflicting sorts of dependency. The extraordinary thing is that he seems to make the most decent, honorable choice open to him.

Unsympathetic outsiders might perceive his actions as strictly selfish, but if this young man is an opportunist, he's also an opportunist with the sensibility of an angel. This is the most complicated kept man to appear on the American screen since William Holden in "Sunset Boulevard," and the role might have been a star-making breakthrough for Walken if the story had fallen into smarter hands. Walken projects a quiet sort of intelligence and emotional strength. You want to know what's going on inside that lean, handsome head and behind that reserved, but alert and incisively expressive presence.

There's some genuine drama and pathos created in the course of the second story, and a feature-length treatment of this particular romantic tangle might have made an unforgettable impression on a vast popular audience.

But after briefly reviving human interest, "Roseland" moves on to a third story so miserably schmaltzy that it undermines the rescue work of the second story.

Mrs. Jhabvala seems to draw on the most expendable relics of her German heritage for the curtain closer, in which Lilia Skala plays a former cook at Schraft's who dreams of winning the Peabody competition at Roseland. She loses her partner, yet goes on dreaming into eternity. Presumably conceived as the height of poetic something-or-other, this episode degenerates into a sentimental blight."Roseland" won't feach the audience that might have responded to its best characters, but perhaps it can serve as a textbook example of how filmmakers turn into their own worst enemies.