Vitas Gerulaitis, who won the Italian Open in an epic final over Guillermo Vilas in Rome Sunday, recovered after losing the first two sets to win his first-round match today in the French Open tennis championships.

Gerulaitis was exceptionally sharp, both from the back court and at the net, as he quickly took the last two sets of a 2-6, 2-6, 6-3, 6-2, 6-1, victory over Butch Walts, the 6-foot-4 Californian who possesses a mighty serve, overhead, forehand and a striking facial resemblance to actor Warren Beatty.

The match had been suspended by darkness Tuesday night with Walts ahead, two sets to one. It was resumed this afternoon on jam-packed court No. 5, one of the eight outside courts at Stade Roland Garros.

A record crowd of 18,000 paying customers crowded into the newly enlarged stadium court and wandered around the grounds today.

Defending campion Bjorn Borg, winner of the world's most prestigious clay court tournament in 1974-75-78, had a struggle on the center court before beating Tom Gullikson, the left-hander of the tennis-playing twins from Onalaska, Wis., 6-3, 7-6, 5-7, 6-4.

Borg, who lost only 32 games in romping through this championship in 21 straight sets last year, has dropped a set in each of his first two matches this year.

He seemed slow and sluggish today, still bothered by the pulled groin muscle that forced him to default from the German Open at Hamburg two weeks ago. Borg did not touch a racket for nine days after the injury, and resumed practice only on Friday, the day before he came to Paris.