Marriott Corp. currently is in the final days of its most successful fiscal year in history, president J. W. (Bill) Marriott revealed in an interview.

He forecast that annnual profits will be up "25 percent anyway" in the 12 months that end this month - resulting in earnings per share of about $1.25 compared with a restated 97 cents in the year ended July 29, 1979, when total profits were a record $36 million.

Sales are running about 15 percent ahead of the previous year, when Marriott voulume topped $1 billion for the first time and totaled $1.026 billion, Marriott added.

Business in recent months has been "excellent . . . it's the best year we've had in five or six years," he said. Moreover, advance bookings and reservations indicate no slump in the next 12 months and the company is not anticipating a major slowdown in the economy or recessin in the next year.

On other subjects, Marriott REVEALED:

A major expansion is planned in the hotel businesses with 10 projected by year's end. A third Marriot in Saudi Arabia will be a 403-room unit in Riyadh, to open in 1981. A Khurais Marriott opens next October and a Dhahran Marriott is scheduled to open early next year.

Overall Marriott has announced seven Mideast hotels and plans seven more under development by 1982 - making it the fastest-growing hotel firm in that part of the world. Marriott also plans hotels in Hawaii.

Some 18 new Roy Rogers restaurants will be opened by Aug. 1 and anothers 30 in the following year - including some in new markets, such as Cleveland. Drive-in order widows are being added at many of the Roy Rogers unit - bringing full circle the Marriott restaurant history of initial curb service that subsequently was abandoned. The ultimate company goal is 50 new Roy Rogers every year.

Hotel room prices are being increased across-the-board by a range of 3 percent to 10 percent, "a catchup mainly" that reflects earlier wage and other costs