Dennis Ralston, the top-ranked tennis player in the United States in 1964-65-66, was sitting in the players' restaurant at Foro Italico, the sprawling athletic complex nestled between the Tiber and a picturesque emerald hill called Monte Mario where the Italian Open tennis championships are played.

Ralston now is traveling the international circuit, playing doubles and coaching six players - brian Gottfried, Roscoe Tanner, Harold Solomon, Dick Stockton, Stan Smith and Bob Lutz - training them as he did when he was captain of the U.S. Davis Cup team.

His window table afforded a panoramic view of the six outside courts at Foro Italico - rectangles of salmon-colored clay marked with white tape, divided into three rows by fences and neatly trimmed hedges.

It was the beginning of lunchtime, and the room was coming to life with the sun that had broken through a thin cloud cover after a hazy, lazy Roman morn.

At Ralston's table, Gottfried and his wife were reading the Daily American, an English-language paper printed in Rome. Tanner was playing with a terrier puppy, the pet of an Italian woman player. Solomon was contemplating his upcoming match against Victor Pecci, the leaning tower of Paraguay.

And Ralston was reminiscing about the first time he came to Foro Italico, in 1963.

"I didn't play in the tournament here that year. Not many Americans did in those days, because most of us were in school and we stayed in the States until after the national inter-collegiates" he said. "But I was on the Davis Cup team, and we stopped in Rome on our way to India. I came out to look at Foro Italico.

"Tennis is a different game over here," he continued."You've got to work on the slow clay to open up the court.You can't argue with the umpires or linesmen, because they only speak and understand English when they want to. You have to accept whatever happens to you because the crowd gets on you if you show your disgust."

Curiously, Ralston could not remember the first time he played the Italian championships.

"I guess I've kind of blotted it out of my mind," he said, grinning sheepishly. "I think it was 1966. I got to the quarterfinals and lost to an Italian. I think it was Nicki Pietrangeli, but it might have been Sergio Tacchini. It's strange, but I honestly can't remember. I may have played here several times, but I can only remember one."

The episode he recalls most vividly was watching his friend Charlie Pasarell play a match in the early '70s against Antonio Zugarelli, the runner-up to Vitas Gerulaitis here last year who was beaten Wednesday by Englishman John Lloyd.

"Zugarelli was just a kid coming up then, Pasarell was an established name, and the crowd really got involved," Ralston said. "They were chanting and whistling, intimidating the linesmen into making calls in Zugarelli's favor.

"Charlie got angry, the crowd got on him, and he was just destroyed. I was sitting in the stands with Erik van Dillen, and we had a recorder.We taped the crowd noise and later played it back for Charlie. You had to laugh and cry for him at the same time."

The tournament was founded in Milan in 1930 after the ascending Fascists became enamored of tennis, a game Benito Mussolini had detested, but re-evaluated after his son took it up. II Duce later played but had his coaches hit only to his forehead since he had no backhand to speak of.

Bill Tilden won the first champion-conceding only five games to the strong willed and flamboyant Baron Hubert de Morpurgo of Italy. The tournament was moved to Rome in 1935, primarily because Mussolini sensed that two Italian players - Glorgio de Stefani and defending champion Giovannino Palmieri - could win and cover his regime with athletic glory.

Instead, an obscure American named Wilmer Hines took the title. The next year Italy was fighting a war in Ethiopia, and II Duce was too involved in this campaign to worry about tennis. The championships were abandoned, not to reappear until 1950.

The present tennis grounds are part of a massive bank of facilities, originally called Foro Mussolini, constructed to host the aborted 1940 Olympics. Hence the accent on sculpture celebrating Fascist ideals of the sporting and military life.

The architect, Piancentini, knew a great deal about grandeur, but nothing of tennis.

He was misinformed as to the dimensions of a court, and so made the playing area in the "Campo Centrale" much too large. Until last year, the runback areas was so vast that it was suggested the ballboys should use bicycles. This year, the area has been cut down by adding box seats.

Piacentini placed the umpire's chair, with its various communications apparatus, on the wrong side, facing into the sun, and the main stadium - which was sunk into a twin crater several hundred yards from the outside courts, but has since been enlarged to 7,000-plus capacity with metal piping and wooden bleachers above ground level - he built out of white marble.

Clay-court epics, great battles of wits and stamina, take on the flavor of passion plays, the vocal crowd choosing its heroes and villains and becoming part of the match as well as the spectacle.

Perhaps it is little wondere Ralston cannot remember which Italian he played in 1966 (it was Pietrangeli). "When the fans start screaming and stomping and chanting in there," he said, "It echoes so loud you can't even hear yourself think."

Despite the stone reminders of Fascist origins, the glory that is Roman tennis dates from 1952, when the championships were vigorously revived by the artful promotion of organizer Carlo della Vida, who set about making the Italian into the second-most important clay-court event of Europe, behind only the well established French championships.