When a baseball team wins 17 of 20 games, it moves into a mirthful fantasy zone from which it knows that it must return all too soon.

So the Baltimore Orioles, who waltzed past Oakland, 3-1, tonight on a three-hitter by Dennis Martinez and Gary Roenicke's seventh homer in 12 games, are having fun while they can. July blahs, August Exhaustion, September pressure: Don't worry, they'll arrive.

For now, the Birds throw paper wads at each other, tell jokes and act like children without a care. Baseball is so simple, they tell themselves, and such fun. Who would be cruel enough to speak the truth?

Tonight Martinez and Roenicke showed how ridiculously effortless the game can appear.

The 23-year-old Martinez, who two-hit the California Angels Sunday, won his fourth in a row with his fourth complete game in his last five starts (ERA in that span; 1.53).

Martinez looks exactly like the Nicaraguan wonder who blew away the American League with a 1.72 earned run average in his last 15 starts of 1978.

"It's so easy for Dennis," said Mike Flanagan, starting an imitation of Martinez's lilting dialect his buddy could hear. "Yes, sometimes Dennis he throw a good two-hitter and sometimes he throw a bad three-hitter."

Martinez, who threw faster in the eighth and ninth than he had in any other inning, just smiled: "I have better stuff than in the two-hitter. I think I gonna be real tough from now on."

Under the tutelage of Ray Miller, the Oriole pitching coach, and the example of his hero, Jim Palmer, Martinez is quickly becoming a polished hurler rather than just a gorgeous diamond in the rough.

His quick progress in learning English has helped. Martinez answers every question like a veteran pitching instructor, analysing sequences of pitches and theory of the game. It is a habit of mind the O's once feared Martinez wouldn't learn until he was 33, not 23.

The Birds will bet the payroll that Martinez will win 20 games. The question is merely how soon. About Roenicke, they are holding their breath. Have the Orioles lucked their way in to a gold mine?

In florida, the O's played Mark Corey ahead of Roenicke.

"They have thought he had something I didn't," Roenicke said. "I can't imagine what it would be . . . yes, they were looking over me to see Corey."

Who could overlook Roenicke now? Batting .338, he has driven in nine runs in this six-game home stand.

Just a month ago Roenicke looked like Frankenstein, after catching a fast ball with his mouth.

"I didn't even want to look in the mirror, it was so awful," he said. "The pitch didn't break bones or teeth - it was a miracle - but it sure busted a lot of flesh and blood.

"I couldn't talk for two days, eat for three or smile for nine. And believe me, everybody was trying to make me laugh and pop a stitch."

Now Roenicke bats with a modified football double-bar face mask.

"I doubt if I'll abandon it the rest of the year," said Roenicke, who crowds the plate and usually was hit by about 10 pitches a year in the minors. "I don't know exactly what's gotten into me. I'm a streak hitter, but this is the hottest I've ever been."

How hot is Roenicke? In the fourth inning with the O's ahead, 1-0, he was fooled by a curve low and away. He flicked the bat at the last moment and hit a high lazy fly to left.

"I was disgusted. I hit it off the end of the bat," Roenicke said. "When got to first, I saw the wind had blown it into the foul pole of a homer. Yeah, it's the cheapest I've even gotten."

"Gary's got the Memorial Stadium stroke," Ken Singleton said. "He pulls everything from the 360-foot sign to the line. He's a member o the 310-Club. That's for guys who hit one in the first row behind the 309-foot sign.

"Don't knock it," Singleton said. "He's figured out the shortest way to paradise."

On his next at-bat, Roenicke, who had three hits, was jammed by a fast ball, yet he dumped a soft line single to center. He scored, for a 3-1 lead, on a hit-and-run single by Rich Dauer and the first hit of Bennie Ayala's Oriole career.

If Roenicke has been living in streak-hitters' heaven, another Oriole has been in a hotter place.

When Mark Belanger singled in the third, he broke an 0-for-31 collar that had made him a 97-point weakling (.097). Four innings later, Belanger beat out an infield single.

Hanging over the Blade's locker was a hand-printed sign that answered the first inevitable question: "They were both fast balls down the pipe."