A major Washington-based developer has made a deal to complete the construction and marketing of new low-rise and high-rise dwellings on the remaining 92 acres of Rossmoor, the 16-year-old Montgomery County senior adult community with more than 4,000 owner-residents.

International Developers Inc., headed by Giuseppe Cecchi, now is the general partner -- with Rossmoor Construction Co. Inc. as the limited partner -- to build and sell the remaining 3,000 dwellings planned for the total 618-acre community at Georgia Avenue and Norbeck Road. Cecchi said yesterday that IDI probably will start a high-rise condominium in 1981 on undeveloped land around the 18-hole golf course at Rossmoor.

Lewis Letson, executive vice president of RCC, confirmed the agreement in which RCC will provide land for new development and obtain a financial return on the basis of sales to future home buyers. Developed land cost usually accounts for 20 percent to 30 percent of a new dwelling. Rossmoor already has 2,700 completed dwelling units, including duplexes, town houses and elevator garden apartments.

Rossmoor notified residents yesterday that it "sought the participation of a developer with proven experience in multifamily residential communities" to assure completion of the master plan with IDI performing the "leading role."

It has been known in real estate circles that the parent Rossmoor group, based in California, had sought for months to sell off the remaining undeveloped land at a price of more than $6 million.

Cecchi said that IDI will provide an initial $500,000 for planning of new development and eventually will put at least $2 million into initial development work.

Seventeen separate condominium and cooperative groups of dwellings already have been completed and sold at Rossmoor over the past 16 years, and three low-rise apartment buildings with 156 units are under construction.

Prices range from $57,000 to $96,000 for the one-, two- and three-bedroom dwellings. Letson said 80 of the 156 units have been sold. Multi-Con has been the builder at Rossmoor in recent years.

A trusteeship of Rossmoor residents owns the common ground, golf course and facilities. Suburban Trust Co. is the trustee.

Rossmoor residents, who must be 52 or older, operate the community with an advisory council that has private management service. Residents pay a homeowner association fee for services and maintenance.