THE ROULETTE wheel spun, its precise clack bending with the losers' moans. The silver dollar plopped out of slot machines. Occasionally a winner's hoot resounded through the chandeliered casino. And, in the midst of all this business as usual at Caesar's Palace, Jane Fonda, dressed to the nines in Hollywood's vision of a network television correspondent, walked around the fringe of blackjack tables.

The film crew of "The Electric Horseman," a romantic comedy starring Robert Redford, Willie Nelson, Valerie Perrine and Fonda, was talking through headphones. The tourists were tripping over the klieg lights. Fonda had a determined look on her face, preparing to bump into Perrine, playing the estranged wife of Redford, a rodeo star. It was planned as a tender, intimate moment.

But, as its freewheeling veterans know, intimacy is not a hallmark of Las Vegas. And when Perrine and Fonda finally met, the sound of cascading nickels and jackpot bells from the slots nearly drowned out their conversation.

"The Electric Horseman," to be released late next year, has the distinction of being the first film made in an internationally-known casino while regular business is going on. "Diamonds Are Forever," one of the James Bond gimmick flicks, used the gaudy exteriors of the Vegas strip - and the cameramen complained that the lights were too bright.

No location, not even New York City's unbridled streets, can be as cumbersome as the lobby and environs of Caesar's Palace. In New York, the passersby are indifferent; in Vegas, they are in hot pursuit of the blinding lights, big names, high times. That's what the city is all about.

As she walked back and forth, back and forth, Jane Fonda occasionally looked up at director Sydney Pollack perched behind a roman column, adding lines of concentration to her exquisitely gaunt face. Once she said, in an out-of-the-blue manner that must be the seasoned actress' instinct, "Slow me down." But she didn't show any acknowledgement or irritation at the 500 tourists giving instant critiques of her performance.

Nor did she react when a cocktail waitress, clad in the hotel's uniform of brief toga, scarlet and silver trim, looked her up and down, sniffed and pronounced loudly, "I didn't know she was so thin."

"Why Las Vegas?" Sydney Pollack, the director now doing his fifth film with Redford and second with Fonda, is eating the Long Island duckling from the crew's chuck wagon.

"It was the title. There is no more plugged-in or wired place in the world. From a visual point of view, it's the best." said Pollack, who, along with Redford, has had the "Electric" property for five years.

The Redford character, Sonny Steele, is the "Marlboro man" of the rodeo world. Five times a World Champion cowboy, he has become dependent on booze and pills and pushes a natural-products cereal for a conglomerate.His sandy, wholesome face appears on its box cover and on billboards.

In the rodeo ring, his gimmick is an electrified saddle and a cowboy suit that lights up. But his life isn't lighting up anymore. His wife wants out. The reporter following his story berates him (before falling in love with him). And he wants out, tired of corporate irresponsibility, tired of pushing cereal, tired of the sedatives given to his thoroughbred.

Vegas was a challenge, just like the changing snow in the Utah mountains on another Pollack-Redford project. "The Saga of jeremiah Johnson." In hurried understatement, Pollack explained, "Its difficult. There's a lot of money generated here. You can't interfere with the business of the town. It's easy to say, 'Close your grocery store for a day' - but a gambling casino."

"Electric" has the uninhibited run of Caesar's Palace, perhaps the town's best-known hotel. Part of the license is due to Pollack's friendship with Caesar's World president, and part to the publicity. The film has prime box-office draws - faces that America recognizes. The sequined and polyestered crowd at Caesar's will not only spread the word about the film, but about the hotel as a place where exciting things are happening.

In the movie, action takes place in every locale of the sprawling complex, and Redford will ride a thoroughbred stallion through the casino. This scene, the dramatic highlight, will be done after 3 a.m. with extras instead of genuine gamblers. But they will film Redford, charging down the neon strip, with the police and reporter Fonda chasing him, at the height of Friday evening traffic.

Redford's decision to steal the horse from the conglomerate is the kind of action Pollack likes: people who do something outrageous to test their moral courage. Those characters filtered in and out of his other films: "Three Days of the Condor," "The Way We Were," "They Shoot Horses, Don't They," "Bobby Deerfield" and "The Slender Thread," his first feature film.

Watching Pollack during the casino scene with Fonda, you could never tell he was flustered. But he was. "It was like being in a nut house, the casino manager was going crazy. I couldn't see. I couldn't hear. I think I was hysterical," said Pollack.

The "Electric" team, from Redford to the message runner, consists of 105 people. They have taken over blocks of rooms at three hotels, plus a motel by the horse trailer. The exact budget was not revealed, but for a start they bought a thoroughbred horse. The cost of transporting, feeding and lodging the crew will be $650,000 on the two locations - Las Vegas until Dec. 13, and St. George, Utah, until mid-February when filming is concluded.

The master of purse-strings and logistics is Ron Schwary, the production manager. Unlike Pollack, he does look harried. "The schedule has changed 15 times and it's only the ninth day of shooting," said Schwary, propping his elbows on his desk. Behind him is a scheduling chart.Peeking from behind his couch is a life-size cardboard picture of Redford, the rhinestone cowboy.

Schwary has just decided when to move a row of slot machines. He has just decided to pay for a suite for some hotel guests, who had been inconvenienced because a shooting had gone over schedule. He had just found out that the trailer he had moved on Saturday - on overtime, because Nevada law prohibits trailer moving on Sundays - didn't have to be moved. "They just changed that scene to Thursday," said Schwary, whose last project was "California Suite." He swallowed a shout.

Redford, Willie Nelson and Timothy Scott were sprawled around the set in a hotel room, arguing about their rodeo life.

Redford was relaxing, ready to growl at his friends. The scene was shot at the Holiday Inn (because it's on the road, somewhere in the Southwest, and "a Holidy Inn is a Holiday Inn, even in Vegas," said Schwary).

"Hey, you look good with the hat on. And I guess you will take it off now," said Pollack to Redford, as he checked the props.

"Where is the Jack Daniels and beer?" Pollack asked. It was set on the table, along with half-eaten sandwiches, a sewing kit, potato chips and newspapers. Pollack started the rehearsal, reading the words of a television commercial that would be inserted later. The three men rehearsed about 10 times. Then Pollack said, "It's beginning to go good."

A break. Redford walked by. Two women in T-shirts were trying to see around the equipment in the narrow hall. "That's not him," said one. "It's his understudy. It's not his nose - I would feel the vibes."

Redford stopped to shake hands with a reporter, who asked about his cowboy character. "We are working it out as we go along," said Redford, who has been developing the unfinished script at nights with the writers. "I don't discuss a character until the movie is over."

Moving along, he stopped to talk with Kenneth Lee, the man who spent more than a month searching for the right horse. Lee's jeans had the cooked-in grime of a ranch hand; Redford's were spotless and pressed. "How's the horse today?" asked Redford, the soft voice muted vet sincere through the thick blond mustache.

The night before, the movie's principals had introduced the horse to the convention center of Caesar's to test his reaction to the lights and to the cowboy's blazing costume, designed by Bernie Pollack, the director's brother. "He's fine," said Lee and the two finished their chat with a very invovled conversation about horseshoes.

Lee wore out a set of tires between Carmel and San Diego looking for the horse. "Stature, regalness - that's a stallion. That's what we wanted. And a good color, we stay away from black and gray. This horse is a blood bay. But what was most important was his disposition. We didn't want a racer, they were too keyed up. All they know is to run."

Lee is very relaxed - this task was nothing new. His father was Wallace Beery's double and Lee himself discovered and trained the horses for Henry Fonda and Glenn Ford in "The Rounders," the television version of "National Velvet" and "Jeremiah Johnson."

Out in the hall, where the hotel maids had parked their cleaning dollies next to the extra lights and microphones, Willie Nelson, country western's hard-hitting legend, discussed his first film effort. "I've learned it takes a long time to make a movie," he said. Next on his agenda is a Universal film based on his album, "The Red Headed Stranger." "So this," Nelson said, "is sort of going to school." When they called him back to the set, he sat on the floor in the same position for three hours before he sang.

Patroling the hall was Mickey Moore, the second-unit director, who started out as a prop boy at Paramount in 1932."I'm doing this film for Sydney, we're friends. I worked with Bob on 'Butch Cassidy,' and Fonda, she's a real professional. She's right on the mark, 10 minutes' warning and she's ready," said Moore.

Vegas presented him problems. "But it's really not frustrating - we are here because it's hectic. There's been one plus. We came in with some real money for the extras to play the slots. And the first extra hit for $250- $300. And that's been happening ever since."