For what? Who needs the aggravation? Why bother?

Tina Kneisley, 19, 105 pounds, 4-feet-10 1/2, of Marion, Ohio, took her roller skates to Nelson, New Zealand, last year and came back with both the ladies' singles and the pairs-skating world championships. Got the medals, brought home the bacon, all the marbles.

So now she's famous, gets the big college scholarship, and the multizillion-dollar pro contract, and all the endorsement deals, right?

Wrong. All rainbow, no pot of gold.

So she's No. 1, so what? What's she going to get, a week at the Capital Centre with The Roller Capades? Holiday on Hardwood?

Says Kneisley: "Some of the adoration that the ice skaters get has rubbed off, but we aren't in their league, exactly. There were a couple of roller-skating shows, but they folded. We can have sponsors, but not many skaters do. The only kind of pros we have are teaching pros."

You think the people from Snyder or Chicago Skate Co. might come through with a free pair now and then? Forget it. She pays about $500 for skates. She sews her own costumes, pays for most of her travel, lessons, rink time. "Thousands of dollars, every year. It's a load on the families."

And frustrating. For one thing, Tina Kneisley says that she does so much more on her roller skates than Dorothy Hamill or Peggy Fleming or Tai and Randy do on ice.

"We can do heel spins. They can't. We can do inside and outside broken ankle spins. I've seen a lot of moves they copied from us."

She used to get up at midnight to drive three hours to Cincinnati for eight hours of lessons starting at 3 a.m. She gave up ice skating, gymnastics, Friday night parties, most of her birthright as an American to a full-scale adolescence. For roller skating. A sport for which not one American college offers a scholarship, she says.

Competition roller skating is harder to do than ice skating, she says. And the skates are a lot heavier. And a lot more people roller-skate than ice-skate, she says, so you'd think the American public would be throwing money at her.

Which brings up the subject of roller skating's image problem.

Admittedly, even here in a Roller Skating Rink Operators Association hotel suite so high the windows look out on nothing but sky, with a baby grand piano and Coca-Cola in goblets, roller skating has an image problem.

"Roller derby," she says.

That sums it all up. Says an association leaflet of roller derby: "The roughhouse skating and violence it depicted in past years is an embarrassment . . . Roller derby types are quickly ejected from modern roller-skating centers."

Back before roller disco, before Linda Ronstadt started skating on California boardwalks, before the 1980 heyday, or the 1960s shift away from the old pipe-railed gymnasium look, roller skating acquired an image.

The image was some guy in a sequined zoot suit cross-stepping backwards at 41 miles an hour through the kids from the church group, and a guy named Shorty or Lefty or Frenchy who handled she-skate rentals, and the mighty Wurlitzer pumping out the Beer Barrel Polka while a reflecting ball overhead sprinkled sullen lozenges of light across paint-flaking, windowless walls. Skating counterclockwise only, puleeze.

In the center would be Tina Kneisley's predecessors working on their figures, their sit spins and outerback camels, but as a sport roller skating got no respect; it was back in the pack with midget auto racing or pro wrestling--roller derby being like pro wrestling on wheels. (Remember? It was always on a TV station that didn't come in very well. Crowds of crouching maniacs battled through the electronic snow, while the announcer kept yelling: "Here's the jam!" which was some kind of formation that meant the hair-pulls and tripping were about to start.)

Now, in the headquarters suite at a rink owners' convention, George Pickard, executive director of the RSROA, says that image is gone. Though it lingers on enough that he'd like to have us say "center," not rink. "It's like bowling alley, or pool hall," he says. They have lanes and billiard parlors now.

"People had been turned off by the dirty, Spartan situation in the roller-skating centers, the pumice blowing around--we used to use pumice for wheel adhesion, but now we've got plastic floor coatings. We've gone to the recreation center concept."

Like Tina Kneisley, Pickard is here for a convention open to all of the 2,300 rink owners who belong to the RSROA, and about 160 exhibitors selling merchandise from urethane wheels to ice cream and slush machines.

This is big business. According to RSROA surveys, there are 36 million indoor skaters in America, skating an average of 6.5 times a year--a figure that is down from the 45 million of 1980, but still 28.5 percent more than the 1978 figure. The average roller skater is 13 years old, Pickard says, adding that his association wants more adults. Such as Tina Kneisley. But how do you find very many idealists of her caliber--people who do this sport not only for no money, but for precious little glory?

"The Olympics," Pickard says. "If we could get in the Olympics, that would mean a lot. We were in the 1979 Pan American Games in Puerto Rico, but we won't be in Venezuela in 1983 because they don't have rinks down there."

"America has the best floors," says the world champion. "In Europe they have hardly any indoor rinks. In Italy you skate on cement. The dust comes up and it gets all slippery."

She ducks downstairs to put on the red skating costume she sewed herself, and fetch her skates to give a demonstration of what it's taken a lifetime for her to perfect, all those 3 a.m. practice sessions. Unfortunately, all she has to skate on here is the hotel driveway, which tilts and bumps, and she has to watch for cars. It's like asking Jack Nicklaus to give a putting exhibition in a pasture. But she's gotten used to a lot of things in a lifetime of roller skating.

She swoops, she spins, she slices impossible parabolas out of the May sunshine. Her reflection slides like water in the windows behind her. The roller skates mutter and grind, hotel guests pause to wonder at her with faces that are smiles and frowns at the same time, faces that study this art and conclude yeah, sure, why not?

Meanwhile, until the world decides to honor her with fame, prestige, or a berth on the Olympic team, Tina Kneisley will keep roller-skating. For the love of it. That's why.