Chris Evert Lloyd, undefeated since she returned from a three-month layoff from tennis, today routed Romanian Virginia Ruzici, 6-0, 6-3, to win her fourth French Open title and complete a triumphant four-week tour on European clay she hopes will give her impetus to do well on the grass at Wimbledon.

Playing with admirable steadiness and determination, Evert needed only 1 hour 29 minutes to trounce the nervous and erring Ruzici in a tedious match on the salmon-colored center court at Stade Roland Garros.

Evert has never lost in 10 career meetings with Ruzici, but today's victory was much easier than her 5-7, 6-2, 6-2 triumph in the final of the Italian Open at Perugia last month. That was Evert's first tournament after taking three months off to recharge her competitive batteries following three lopsided defeats in two weeks at the bands of teen-ager Tracy Austin in January.

Since returning to competition, Evert won 15 consecutive matches on the slow clay that is her best surface: five in Perugia, four at Berlin, where she helped the United States to its fifth consecutive victory in the Federation Cup team competition, and six here.

Evert is expected to win on clay.She has won 34 matches in a row on that surface since May 1979 and 159 of 160 matches since the summer of 1973. Her only clay court defeat in 6 1/2 years was to Austin in the semifinals of last year's Italian Open.

With Martina Navratilova and Austin, 17, the two players ranked above her, bypassing the Italian and French opens this year, Evert was the odds-on favorite. But she had self-doubts, some of which have now been removed.

"It's a good moment for me, because I think I surprised myself coming back," Evert said after receiving the champion's trophy and a bouquet of flowers in the Presidential Tribune after the match. (The first-place check for $43,000, which the French consider secondary to the prestige of the world's premier clay court title, was presented later, in privacy.)

"I haven't lost a match in four weeks playing, so in that respect, my confidence is restored somewhat," she said. "Right now I'm thinking about Wimbledon. I needed to win these clay court tournaments to gain the confidence I had lost. Now I feel good about my game. I'm looking forward to playing on the grass, even though it never has been that well suited to my game."

The men's singles title will be decided Sunday when Bjorn Borg plays Vitas Gerulaitis, who has never beaten Borg in 18 meetings.

"I'm going to try and do something different, but I've tried about 30 different ways to play the guy and none of them have worked," Gerulaitis said after his five-set semifinal victory over Jimmy Connors. "I'm looking forward to it, because this is the best I've played on clay for a while . . . I'm just going to relax and do the best I can."

Borg, who has lost only one match on clay since 1976, is an overwhelming favorite to become first man to win the French title three years in a row and five times overall. He has lost no sets and only 31 games in reaching the final, and takes a 37-1 record for the year into the title match.

Ruzici won the French title in 1978 over a field weakened by the absence of Evert and the other top women who were then playing World Team Tennis in the United States. She said beforehand that she had been dreaming all year of holding aloft the winner's trophy at Roland Garros. Her dream turned into a nightmare today.

Evert kept her pinned to the baseline with deep ground strokes, keeping the ball mostly on her vulnerable backhand, and sprinkled in a few excellent drop shots in running off the first eight games to take complete control.

Ruzici had three game points in the second game, three in the sixth game, and two in the eighth, but couldn't win any of them. She made far too many errors on the backhand and, overeager to run around and thump her formidable topspin forehand, was overhitting from that side as well.

Early in the second set, she tried to break up Evert's rhythm by hitting soft and sometimes short, taking pace off the ball, but she had little success with that tactic.

"I tried to change the situation by changing a little bit the game, but that didn't work either, said Ruzici, a slender 25-year-old who is nicknamed "Gypsy."

"I felt a little bit tired, even from the third game of the match. If I had won that long second game, maybe I would have gotten into the match. But she was keeping me deep, moving me around. Nothing I tried was working. When I came to the net, she passed me every time."

Ruzici finally broke serve to win the third game of the second set when Evert double-faulted to deuce, got a bad call at the baseline and netted a forehand.

But Ruzici lost her serve again in the next game, going into the doubles alley to run around her backhand, but overanxiously netting the forehand.

It was, all things considered, a dreadfully boring match for most of the approximately 14,000 spectators.

"I can see why the French are sexist about women's tennis," said one disgruntled Australian at courtside.

"A match like this ought to send them back to Court 10. The thing that bothers me most is that every time I fall asleep, some fool applauds and interrupts my nap."

Evert didn't seem to mind that the match lacked drama. She was pleased to get it over with a hurry.

The tournament had started off badly for her. Through a mixup in communications, she was not met on her arrival in Paris as expected. Then she walked off with the wrong suitcase, and didn't realize it until she got to her hotel, opened the luggage, and found it full of clothes belonging to an Argentine man.

But everything worked out all right in the end. "It's funny how things turned out, because I never felt on top of my game this whole tournament," she said. "I felt I was struggling for two weeks, and Virginia was playing really well. I really didn't expect to win the final this easily."