Eight hundred adoring fans looked on as Gloria Swanson, age 81, was wheeled into the spotlight at the Shoreham ballroom yesterday. Swathed in fur tails and hiding behind dark glasses, the diminutive movie queen clutched a half-gallon of gin in one hand and a cane in the other.

Without warning, Swanson leapt up on stage, surrendered her gin and furs and mock-tipsily crooned, "Hello everybody," and proceeded to parade around the room to the tune of "When the Saints Go Marching In."

So began the Circus Saints and Sinners annual Christmas roast, which has taken on the likes of Henry Kissinger, Elizabeth Taylor and Carol Channing. While the guests munched on chopped sirloin and lemon chiffon pie, "fall gal" Swanson nibbled at two bran muffins with raisins, a banana and an apple, washed down with bottled water.

But on with the show.

Skit one. Two movie barons (supposedly Bob Evans of Paramount and Jack Valenti of the Motion Picture Association) are trying to find someone to accept the Female Entertainer of the Century Award. Ronald Reagan is getting the male award, but Nancy has declined, they say, "because she gained six ounces in the campaign and she is back on the Scarsdale diet."

The stars being considered for the award are Liza Minnelli, Shirley Temple and Liz Taylor, represented by a zaftig actress looking divine in a chiffon dress and chomping a mammoth turkey leg. By the end of the skit, Swanson manages to choke the characters one by one and claim the award, saying, "I accept. But there must be no meat and no sweets at the banquet, and most of all, no Kennedys."

Skit two. A parody of Norma Desmond's final scene in "Sunset Boulevard." Reporters are gathered in Swanson's apartment for the introduction of her autobiography. "I suppose if Laurence Olivier can make TV commercials," one says, "Gloria Swanson can peddle her book at Brentano's." Next thing you know, Swanson, in a red chiffon scarf and carnation, is at an autograph party. "All right, Mr. Pulitzer," she sighs, "I'm ready for my prize."

Then came radio personality Eddie Gallaher, who promised to recount Swanson's autobiography, "from infancy to adultery."

All in all, the roasters didn't do too much damage to Swanson. "Underdone," said Father Gilbert Harke of Catholic University when asked what he thought of the roast. "Processed by microwave."

Swanson was presented with a check for her favorite charity (the Salvation Army) by Barnee Breeskin, president of Circus Saints and Sinners, a businessmen's fraternity which raises money for charity. Breeskin then presented her with a congratulatory letter that President-elect Ronald Reagan had signed "from one late show trooper to another."

Swanson, unscathed and looking elegant in an apricot-colored, handpainted silk dress with matching coat, mink hat and silk pumps, climbed on a stool and thanked the group for their "laughter and love."

Then came the crowds, who wanted signed programs and copies of "Swanson on Swanson" for Christmas gifts for mothers-in-law. She obliged graciously. o

"I've never been roasted before," she said. "But I'd do it again. It was lovely." She said her goodbyes, with glistening eyes, and with her entourage walked to her limousine waiting to whisk her back to New York.

"Everybody treats me like an old lady," she barked, shaking off several men who offered her an arm. "I'm sick of hearing things like, 'Watch out for those steps.'"

Swanson's companion took a cooler filled with apples and muffins out of the trunk in case she wanted a snack for the road. Waving aside all assistance, Swanson bounced into the back, adjusted her leopard-print pillow and blanket, and was off, without even a singe from her roasting.