Late-night television is developing into a tootsie-frutsie world all its own, something of a haven from the wan blandness of prime time. But this revolution may turn out to be very short-lived.

"Roadshow," the series pilot to be aired by NBC in the Saturday Night Live" time slot at 11:30 tonight on Channel 4, was rushed onto the air partly because the new cast and staff of "Saturday Night Live" have turned out to be, to judge from their work, a witless tribe of philistines. They dropped a bomb in the 12-megaton range, and insiders say that network ad salesmen are having a hard time getting sponsors to place commercials on the program, which used to sell out months in advance.

Originally, "Roadshow," which hatched in the maverick mind of Craig Kellem at Twentieth Century-Fox Television, was a candidate to replace "SNL" on the fourth Saturday of each month, the way "Weekend" once did. Now it's possible that "Roadshow" and other projects are candidates to replace "SNL" every week. What was once NBC's monopolistic domain has suddenly become a shambles.

Unfortunately, the NBC censors have jumped all over "Roadshow" because of jitters they got from the disastrous first two editions of the new "SNL" and the hundreds of angry phone calls they provoked. "Roadshow" is an inquisitive and rambunctious TV magazine, one that mixes impromptu comedy and what a producer calls "improvisational journalism." The censors were particularly nervous about sequences involving "the real Animal House" -- a hell-raising fraternity at Louisiana State University -- and a prolonged peekaboo at a sensuality seminar in New York.

Their concern isn't exactly incomprehensible. The sensuality segment has a pack of naked women (seen from the shoulders up) taking lessons in self-arousal from a body-conscious therapist. "Okay, so let's plug in the vibrators and get it all going here," she says at one point. As it turns out, the "vibrators" are innocuous mechanized massager things -- nothing very naughty about them.

However, decreed one NBC censor, the mere word "vibrator" is verboten on NBC, which the censor referred to as "my network." These censors can get awfully territorial. Apparently abou 90 seconds of the program has been eliminated, even though there was nothing in the segment that hasn't been talked about on the "Phil Donahue Show" until one and all were blue in the face.

(Ironically, the program department at NBC liked the sex therapy segment and moved it up from its last-placed position in the original show, even as standards and practices was going at it with a scalpel.)

"Roadshow," though an occasionally uneasy mix, has fairly irridescent possibilities. The idea was to put a bunch of merry-macs in a bus and send them out to document the American fringe for the fringe-viewers of late-night TV. The program allows viewers to decide for themselves whether they are delighted or disgusted by the wild "Dekes" of LSU's fraternity or the naked ladies playing Tickle-Me-Pink, but it's hard not to be at least slightly fascinated and impossible not to recognize signs of the times.

The fact that producer Chuck Braverman and his staff left to the viewer's discretion the option of tolerating or deploring the material viewed (it includes a bizarre San Francisco nightclub act involving a man, a woman and an 11-foot snake) is probably what upset NBC censors. You can trot all the sin you want across the TV screen as long as you maintain a pose of umbrage and disapproval.

Indisputably the high point of the program, however, is one of its purely uncontroversial, scripted comedy bits: th brilliant Don Novello back in his "Father Guido Sarducci" togs and singing "MacArthur Park" in Italian. You probably have to know the lyrics to appreciate the charm of this, but those who do will relish the fact that songwriter Jimmy Webb's banal imagery about a cake in the rain has been made gloriously literal.

The LSU segment has a great deal in common with a later stop at Carbondale, Ill., where 20,000 people celebrate Halloween in get-ups that range from an eyeball to John the Baptist; there are also "96 ayatollahs, a lot of Muppets and quite a few Ronald McDonalds," a reveler notes.

A bearded man dressed as an orange thoughtfully tries to justify the wild abandon. "We're young now," he says, "and we might as well be as crazy as possible." A fraternity brother interrupts the food fights to explain that this is "like Never-Never Land, where you never grow up," and another brother notes proudly how he placed a Deke pin on the corpse of a member who had died of cancer.

Small-talk sessions aboard the bus bridge various segments, not always with great finesse. Guest host John Candy is a decided, felicitous asset, however, and at least the cast of zanies is an improvement over the snide, smug little rich kids on the new "SNL."

Singer Tom Waits is an acquired taste who may send viewers scrambling for the channel-changers during his two sequences on the program. During one of them, when Waits is interviewed by an unseen colleague, a portion of the screen is blacked out. Behind that obstruction is John Belushi, who is a friend and fan of Waits'. But after the segment was taped Belushi's manager reminded him his new movie contract rules out TV appearances. Hence no billing and no visible Belushi.

The original "Saturday Night Live" opened up late-night to new kinds of programming and new audiences, including an uncountable number of video expatriates who were fed up with the plastic fantasies of prime time. But the small minds that run TV, instead of fostering further experiments in late-night, merely tried to clone "SNL."

First came ABC's smarmy, self-congratulatory, rigorously unfunny "Friday's," a program on which the axe of cancellation is widely expected to fall any day. Now even "Saturday Night Live" is a bad imitation of "Saturday Night Live." Insiders say pandemonium, always the order of the day at NBC, now extends into the "SNL" time period, once a source of little but revenue for the network.

What may happen is that the audiences attracted by the novelty of the old show will simply drift away from late-night TV, as disillusioned with it as they are with prime time. Or new, promising projects like "Roadshow" may result in a replacement for "SNL" that is a true departure and not merely an insipid Xerox copy.

As a TV veteran has said, the only way to get anything really different on the air is by conspiracy. The aim of the networks, in their timidity and mediocrity, is to become conspiracy-proof; the bright young producers of this world have their work cut out for them.