Ross Cortese, the man who pioneered in the creation of all-adult communities in California and even proved the validity of his concept in this area, is a frequent visitor to Washington. He comes here about once a month, as chairman of the board and chief executive officer of Rossmoor Construction Corp., to inspect and direct operations at Rossmoor Maryland, the over 50 community that now has more than 3,000 residents in 2,300 dwellings on a 950-acre tract opposite Manor Country Club in Montgomery County.

Cortese, who has been visiting here for the 15 years since Rossmoor opened, reluctantly agreed to an interview in the Rossmoor dwelling that he uses as an office and home away from home. He and his wife and daughter live in Arcadia, Calif.

Several Washingtonians who have known Cortese over the years agree that he is brilliant, inspring, exceptionally hard-working, genuinely modest and also mercurial - even likely to explode some times.

"He's totally preoccupied in what he is doing and is generally considerate of people - but he can raise hell, too," said long-time friend Oakley Hunter. Now chairman of the board of the Federal National Mortgage Assoication here, Hunter set up original FHA financing for Rossmoor 20 years ago as a private attorney on the West Coast. Now Rossmoor units are conventionally financed.

But let Cortese speak for himself:

"I'm not a genius. What you do is more important. We are proud of our communities and we like Washington. It's really beautiful. And the market has responded to out product - secure, modest housing for adults who like have a wide range of recreational and social activities, plus health care facilities. But the government has permitted housing costs to get out of hand. It's getting tougher and tougher to be a developer today. Assembling the acreage we have here and developing it would be out of the question now."

Cortese also revealed that Rossmoor Maryland is responding to rising costs by making changes in its housing product. Conceding that market response to a new line of model luxury apartments has been tepid recently, he said that a switch will be made, probably to eight-story apartment buildings with apartments in the $40,000-$60,000 range, plus other forms of clustered dwellings.

"Our new (now discontinued) models were gorgeous but we've got to please the masses and meet the market. The new basic dwellings will be 800 to 1,200 square feet without any marble frills or angular rooms. Then the buyers can do their own thing with them," he said.

Disdaining to talk about himself, the developer also conceded that it was a "dumb thing" for the firm to go to public ownership in the early 1970s. Financial pressures caused that move. In 1969 and 1970, Cortese almost sold out his Rossmoor holdings.

"But our buyers have a fine record," he added. "No mortgage delinquencies and no foreclosures in nearly 20 years. And that includes 32,000 dwellings that we have built and sold." One reason is that most of the Rossmoor buyers in California and Washington have been mature couples who sell more expensive houses before moving to a Rossmoor. Nearly 50 per cent of Rossmoor buyers have been able to make all cash settlements and most of the others make substantial down payments and have smaller-than usual mortgages.

The 1977 Rossmoor financial report shows that, "due to substantially increased residential deliveries in Maryland," Rossmoor "achieved profitable operations for the first time since its inception eight years ago. Net income was $306,000 or 9 cents a share on revenues of $33,3 million, as compared with a prior year loss of $3.1 million or $1.01 a share on revenues of $7.4 million."

During fiscal 1977, Rossmoor delivered nearly 400 residential units in Maryland "compared with only seven a year earlier when development was restricted by a sewer moratorium." Rossmoor recently spent millions to build its own sewage treatment plant.

RCC plans to continue building and developing at Rossmoor Maryland for another 10 years at an overall density of 10 units per acre. In addition to green areas, the site includes an 18-hole golf course that has been in use for a decade. And an 18-acre site near the Rossmoor entrance has been reported sold to Ward Development Corp. of Gaithersburg, which plans to start a medium-size shopping center this year.

Cortese recalled that the front-end cost of getting Rossmoor Maryland under way in the early 1960s was $7 million, exclusive of the land, which cost $4,500 an acre. "Everyone thought. I wascrazy to pay that much," Cortese said. Now it's utterly impossible to find good land at an affordable price, and the cost of the backbone of a new development is terribly costly because of increased financing expenses."

Contending that he'd "be delighted to move in" a Rossmoor adult community in California (where several have been completed) or in Washington, Cortese remains convinced that his quasi-retirement-community concept is more viable than ever. "Older people want to stay near their families," he said. "And our plan enables them to have carefree home ownership and the security (guards at the gate and patrols on the property) one seeks in later years."

When he visits Rossmoor Maryland, Cortese brings Albert R. Ceresa, a younger man who serves as president of the parent firm. Ceresa joined Cortese in 1963 after being a mortgage banker in California. On the job here is Lewis M. Letson, executive vice president, who serves as project manager. He said that the new residential product will be availble later this year and that sales of nearly completed semidetached houses and apartments in three-story buildings will continue. About 40 are left. He added that there is a backing of about 125 undelivered dwellings on which deposits have been made.

Cortese, Ceresa and Letson agreed that they are working hard to get rid of the delays in deliveries of sold houses. "But the past two winters have been really tough on outdoor construction," Letson said. "So we are now thinking about steel-frame construction with concrete panels (made off-site) that could be placed in cold temperatures."

Before leaving recently to return to California, Cortese said that he defies anybody to be happier than most Rossmoor residents. He seemed almost to envy his perception of their lives. Cortese, 60, its trim and of medium build. Tanned and dressed in a black turtle-neck shirt-sweater and maroon sweater, he wore leisure slacks and black shoes. His large diamond ring was the only conspicuous item in his attire. He didn't smileoften.