Betty Rollin, a network television correspondent, had to pick up the pieces of her life after an operation for breast cancer. Instead of just picking them up, Rollin flung them, bruising and mystifying many of the people around her.

Mary Tyler Moore, who makes her dramatic television debut tonight as Rollin in "First You Cry," a two-hour movie on Channel 9 at 9 o'clock faithfully portrays a woman at a point of terrible self-doubt and confusion. Given the popularity of the Emmy-winning Moore and the topicality of cancer (one in four Americans will get some form of cancer in his or her breast cancer), the drama is likely to in the wintertime, weath, an open find a wide audience.

Its success results from an even exploration of human emotions, not only in the vulnerable Rollin character, but also in the emotional neutrality of her husband, played by Anthony Perkins, and in the generous opportunism of her lover, played by Richard Crenna. Its downfall rests on the neatness of the story. The old sweetheart returns when life is in the pits, offering lilacs in the wintertime, walth, an open promise of love and a bedroom with a crackling fireplace. Perhaps Rollin was lucky.

"Cry" is based on Rollin's own frank 1976 best seller, but director George Shaefer and his team manage to avoid the cliches and oversimplifications that loom in any story about a contemporary woman and her bout with cancer. They avoid the soap opera slick and the medical center tech and boil the story down to a straight-forward examination of relationships under strain.

The story starts with Rollin on the job at NBC News, reporting on breast cancer. Her documentary includes a glimpse of Nelson and Happy Rockefeller, who along with former first lady Betty Ford help usher in the era of cancer candidness. A few hours later in the movie, Rollin and her author husband are in bed and he announces that the lump in her breast is getting harder. After some resistance Rollin promises to have an examination before an assignment in California. The doctors discover a maligancy and remove her left breast.

There are ample hints at marital problems that preceded the surgery. Her husband doesn't want to kiss in public, and she accuses him of admiring "the Wonder Woman types." But there's a twist: He doesn't reject her after the surgery. She freezes up, refusing to give his own rigidity a chance to defrost, or to accept his attempts at consolation.

The lover is waiting, casting aspersions on the husband ("you need someone to tell you you can cry"), and offering a chauffeur, maid and compassion. Finally the only rehabilitation for Rollin is writing a book. Only when that is completed does she decide on her new role, alone, pledging peaceful non-coexistence with her husband, and enjoying prominence as a best-selling author and a working woman.

While the treatment of cancer is a departure, most of the acting falls into familiar professional slots. Perkins, who is appearing in a dramatic television role for the first time in 10 years, portrays his usual haughty, insecure individual. Crenna appears safe, thoughtful.

Moore may not be Katherine Hepburn, but she is capable in the role. Every 30 minutes she breaks down and says, "I'm sorry," revealing a new side of the Rollin character, a woman taught never to show weakness.

Yet here Moore's familiar extroverted manner comes in handy in depicting Rollins' attempts to be brave. But she also can portray the private misery. Her pained expression when she can't open the toothpaste is a small dramatic triumph, and she plays the bigger scenes well too, as when she walks into her husband's book party to hear him demand to know why she is late. He hasn't taken into account the hard decision of what to wear for her first appearance after surgery. "I'm not the terrific, gutsy Betty anymore! I'm damaged goods!" she screams, an understandable reaction.

"Cry" isn't all hysterics, long pitiful looks into the mirror and domestic troubles. In one very humorous scene, Rollin and her best friend, Erica, go into a button shop looking for a 'nipple' for her artificial breast. They touch all the buttons and finally decide on some wool fringe. That's a frank moment that must confront every breast cancer victim.

The movie ends with a message. As the Rollin character returns to work, her office television screen plays one of her own interviews, in which she gives some advice: "The trick is to live as if you're going to die, and then not die." But she admits, "I haven't really got that down yet."