In less than three years, Rosalynn Carter has gone from the Blue Room to the board room.

Yesterday, the former first lady was elected to the board of directors of Gannett Co. Inc., the giant media conglomerate that includes USA Today and over 80 daily newspapers as well as six television and 13 radio stations, among other concerns.

"Rosalynn Carter brings to Gannett a very valuable perspective from her unique experiences in the public sector and from her civic and business activities in the private sector," board chairman and president Allen H. Neuharth said in a statement issued yesterday in Boston. In that role, he said, she can "have a significant impact on the news and information business in the USA." Neuharth was unavailable for comment yesterday.

Asked which business activities were being referred to, Gannett's vice president for corporate communications, Walter Wurfel, said that "of course she's been a manager of their family business in Plains" and in addition she "has been focusing on issues concerning the mentally ill, the elderly and women, working with problems of communities to build a more caring society." As for what the "significant impact" might be, Wurfel said, "I never try to interpret the words of my chairman."

Said Wurfel: "In terms of purposes," Neuharth's statement "will have to speak for itself." He added that Rosalynn and Jimmy Carter "had attended a luncheon our board of directors had in Atlanta a couple of years ago, so she has known our chairman for some time."

Rosalynn Carter said in a statement yesterday that she would "do my best to make a significant contribution to this fine organization." And that, a spokeswoman in her Atlanta office said yesterday, "is all she plans to say about it at the moment." Carter, who has no other formal business affiliations, will attend her first board meeting in October. Meanwhile she is spending her days at a word-processor, completing the autobiography that Houghton Mifflin will publish next year.

Gannett's directors receive an annual salary of $17,500. With the addition of Carter, 56, there are now three women on the 14-member board.