NEW YORK (AP) _ Sterling Drug Inc. today rejected as ''grossly'' inadequate the unsolicited $4.2 billion buyout offer by Swiss pharmaceutical giant F. Hoffmann-La Roche and Co., and said it was in talks with other potential acquirers.

Sterling announced its board of directors unanimously had decided to recommend that its shareholders reject the $72-a-share tender offer as not in their best interests.

The board determined Sterling would be better off in the long term by remaining independent, but the company was involved in negotiations regarding a possible acquisition by a third party in order to protect its options.

Sterling shares jumped $3.25 to $77.37 1/2 a share after a delayed opening today on the New York Stock Exchange, signaling that speculators expected a bidding war for the drug company.

John M. Pietruski, Sterling's chairman and chief executive, said the board reached its decision based on a number of factors, including the opinion of its advisers that the Hoffmann-La Roche offer was financially inadequate.

Pietruski indicated that negotiations for a possible acquisition by a third party depended on Hoffmann-La Roche's future actions regarding its bid, and that talks could be terminated if the hostile suitor withdrew its offer or it otherwise was halted.

The Sterling board indicated it intended to pursue the U.S. District Court lawsuit it filed last week, which seeks to block the tender offer on the grounds that Hoffmann-La Roche violated federal securities laws in making its bid.

Sterling alleged that the Swiss company failed to follow federal disclosure requirements and that two of its wholly-owned subsidiaries engaged in illegal insider trading using advance knowlege of the offer.

Hoffmann-La Roche has denied the allegations.

Sterling spokespeople declined to comment beyond a company news release announcing the board's decision. A Hoffmann-La Roche spokeswomanm in New York said the company had no immediate comment.

Separately, Hoffmann-La Roche reported from Basel, Switzerland that it expected higher profit for 1987 than in the previous year, despite a 1.3 percent decline in sales.

Group sales fell to 7.7 billion Swiss francs, about $5.62 billion at current exchange rates, in 1987 from 7.8 billion francs in 1986. A news release stated the sales drop was due mainly to the strengthening of the franc against the U.S. dollar, and when measured in local currencies Hoffmann-La Roche's sales rose 14 percent during the year.

The company de PM-Business Mirror, Adv 19,0688 $adv 19 For Release PMs Tuesday Jan. 19 Small Riverfront Firm Does the Thinking for You Eds: John Cunniff is off today. By DANIEL J. WAKIN AP Business Writer

NEWARK, N.J. (AP) - Ever say about a new product, ''Gee, what a simple idea. I could have thought of that?''

A company in Edgewater, N.J., says it - and does it.

Innovations & Development Inc. trades in the currency of ideas as a consultant on new products for major corporations.

Sitting across the Hudson River from the towers of Manhattan, the firm generates ideas for new products and finds new uses for old technology.

''We're trying to generate products that will be meaningful to the market,'' said Gary Grossman, the company's president.

''We will not invent a laser beam, but what we will do is take a laser and make it into new product,'' he said.

Innovations & Development manufactures no products, but approaches clients with ideas, consults on the engineering of new goods and collaborates with product development departments. Most of its patents are held by the clients.

The 23-year-old company, which has $2 million in revenues a year, designed a socket wrench that stores its own sockets; a simplified sailboat for under $1,000; a wall-mounted rechargable flashlight; and an exerciser that reproduces arm motions of an orchestra conductor or traffic cop.

As an example of how they come up with a product, Grossman and his partner, Edward Meisner, were pondering what they could do with hot-melt adhesive - glue that needs to be heated up to stick.

After six months of research, they came up with the idea of using it to hang things on walls. Within three years, they had the Hang-Fast device, made by Parker Group Inc. of Northboro, Mass., and sold by Sears, Roebuck and Co.

Essentially, the device heats up discs backed with adhesive. Affixed to the wall, the disc can hang up to about 30 pounds.

It works on tile, formica and sheet-rock without causing damage when removed by reheating, Grossman said, something the firm's market research found homeowners wanted.

''It's a very easy thing, but it took us a lot of thinking to get there,'' he said.

Innovations & Development worked closely with Parker in developing Hang- Fast. Most of the technical work was done by the Massachusetts hardware manufacturer, said John Trebel, a marketing vice president for Parker.

''To develop something like Hang-Fast, you have to have a certain amount of thinking time available,'' Trebel said. ''Rather than having a lot of engineering, marketing, advertising people hanging around, we use IDI.''

Grossman said his staff is working on about 12 projects, about all they can handle at one time. Broadly, many of them concern heat sources.

''We're looking at irons in terms of the next generation of irons,'' he said. ''We want to make it easier to iron, and more fun, actually.''

Grossman offered no details, noting that the project is in a preliminary stage.

Other areas of interest are butane as an alternative to electricity and batteries, and more specialized uses of microwave technology. Innovations & Development is also seeking safer ways to provide chemotherapy.

Grossman bristles at the suggestion that his business epitomizes the future of the U.S. economy as shifting from manufacturing to service-related .

''I don't buy it at all. Oh my God, are we manufacturing like crazy. Just go to the Midwest,'' he said.

As he sees it, Innovations & Development is merely fertilizing the ground of industry.

For instance, he provides this scenario:

''The transistor is dead. Some genetic engineering company discovers how to grow memory, literally like a brain.

''Who's in the forefront of genetic engineering? America. All of a sudden we have fields of memory banks. We don't need transistors,'' he said.

''You might say that I'm crazy, but I can see America through the biological area growing buildings.''

Grossman likes to plan ahead.

End Adv PMs Tuesday Jan 19