AMERICAN INTEREST in tracing ancestry overseas has been running high since the "Roots" fever inspired by the television series based on Alex Haley's novel, but the U.S. Bicentennial celebration provided an even bigger boost, according to Donna Hotaling, a noted genealogist of Vienna, Va.

"Someone in almost every family is doing some kind of genealogical research," said Hotaling, executive secretary of the National Board for Certification of Genealogist of the United States and Canada. "The Bicentennial stimulated people try to place their ancestors in our history."

Britain and Ireland are the main focus of attention because of historical links to the United States and the advantage of a somewhat common language, she explained. But other northern European countries are not far behind as targets for the seekers of forebears.

"There always has been considerable interest in Germany and the Scandinavian countries," she said. "There is also interest in France, and recently, Poland."

Genalogical travel is largely done on an individual basis, partly because of the difficulty of putting together large groups with identical areas of interest.

"It's almost impossible to organize a profitable-size group wanting to go into one particular area," said Warren Mitchell, a retail travel agency executive in Long Beach, Calif. "None of the wholesale tour operators is offering this kind of business."

One national tour operator attempted to capitalize on ancestor-hunting at the height of the "Roots" craze. "We gave it up two or three years ago," said a spokesperson for Four Ways Travel, 950 Third Ave., New York. "It didn't go. There just wasn't enough demand."

Hotaling cities another reason. "The commercial travel companies can't do it," she said. "They are geared to make the travel arrangements, but they don't have the expertise in genealogy."

Hotaling conducts small groups of serious seekers on genealogical tours, concentrating on Scotland, Northern Ireland and the Irish Republic. The groups are limited to the number of people that can fit into a hired mini-van, which she drives while teaching the tricks of the trade.

"Most of my clients are amateur genealogists who are getting their feet wet by tracing their own ancestors," she explained. "I take them first to the registry centers in Dublin, Belfast or Edinburgh, then to the sites we locate."

Others doing similar work in the Washington area include William Linder, director of genealogy for the National Archives, and Lorraine Branning, an expert on Germany in the Archives' department of education.

"They're both good friends of mine." Hotaling said. "Occasionally we pony each other's tours by linking them head to tail."

A prerequisite for participation in the guided tours is personal research to trace U.S. ancestry back to a specific locality and time frame for emigration from Europe. Hotaling highly recommends the extensive records of the Genealogical Library of the Church of Jesus Christ of Latter-day Saints in Salt Lake City, which maintains 348 branches throughout the United States.

The branch libraries have access to more than 100,000 volumes of family genelogies containing 50 million names, and more than a million rolls of microfilmed records collected worldwide since 1938. Use of these facilities is open to the general public. At present, the Mormon Genealogical Society has 13 camera crews photographing old documents in North America and 67 more roving through Europe, Asia, Africa and Central and South America.

"The centralization of these records is a great advantage," points out Mrs. Douglas McLaughlin of San Pedro, Calif., a longtime worker and supervisor in the Los Angeles Temple library. "For example, if you were researching Danish ancestry on the scene, you probably would need to travel to several different locations. We have 90 percent of the available Danish records on microfilm.

"Interest in Denmark and Greece is building up right now. We've had recent workshops on Transylvania, Japan, Korea and Hawaii. The showing of 'Holocaust' on TV also brought a great many inquires from families of European refugees of the World War II period."

Washington-area sources of genealogical information include the National Archives, the General Archives Division in Suitland, Md., the Library of Congress and the National Genealogical Society. Leaflets describing these services may be obtained free from the General Services administration.

A list of professional researchers who work for a fee is available from the Board of Certification of Genealogists, 1307 New Hampshire Ave. Nw, Washington, D.C. 20036.

Hotaling is an additional source of genealogical and also other countries. For a fact sheet on how to order, write to her at 2255 Cedar Lane, Vienna, Va. 22180.