Nancy Reagan's departing chief of staff, James S. Rosebush, said yesterday he will open his own consulting firm here to advise foreign firms, governments and foundations about public affairs, community relations and Americans' perceptions.

Rosebush, who will leave his $72,000-a-year post next week, said he also hopes to work along similar lines with U.S. firms and foundations.

"I haven't signed anything yet but I've been talking to potential clients and they to me," said Rosebush, 36, who has a graduate degree in public affairs from Boston University and who once had his own consulting firm in Boston specializing in corporate community relations.

In November, Rosebush unexpectedly announced his intention to leave the White House, saying, "I really haven't given much thought to what I'll do next." He said he had decided it was "time to leave" since he would soon be in the post four years.

Like his former mentor at the White House, Michael K. Deaver, who opened his own international consulting firm last spring, Rosebush greatly expanded his foreign contacts by advancing Mrs. Reagan's activities on the Reagans' trips abroad since 1982.

As a result of those trips, Rosebush said, he gained "insight and training in dealing in the international arena with top leaders in government and business. It's probably the best way to learn -- at the highest levels -- and that experience can be useful to U.S. corporations interested in recognition abroad."

Rosebush said he told Mrs. Reagan he plans to open his own firm but did not discuss it with anyone else, including Deaver. He said he expects to move into offices in the law firm of Ward, Lazarus, Grow and Cihlar at 1711 N St. NW within the next few weeks.

You can call a party exclusive when it's thrown by Walter Annenberg for Prince Charles and Armand Hammer isn't on the guest list.

In fact, Annenberg and his wife, Lee, will entertain only 40 couples at a dinner-dance next month when Charles visits Sunnylands, their Rancho Mirage, Calif., estate, in connection with a youth leadership project called "Operation Raleigh." Annenberg is honorary president of "Operation Raleigh" and Charles is its patron.

The lucky party goers will be the first 40 to respond out of the 150 prominent couples invited from around the country. With exclusivity, of course, comes obligation -- $25,000 worth of obligation, to be exact. That's how much tickets will cost, but considering the fact that with Charles comes Sunnylands, it may be one of the benefit bargains of the Rancho Mirage season. Getting an invitation to the Annenbergs' desert fiefdom is still one of the coveted symbols of arriving socially.

Charles "arrived" the first time in 1974. On that occasion, he took one look at the exquisitely manicured nine-hole golf course, then asked for a driver and a golf cart and drove around hitting golf balls.

Annenberg, who is more than a little fussy about his course and who has been known to refuse permission to professional golfers like Lee Trevino because of the divots they take up, couldn't have been more forgiving of Charles.

"I don't care about that," he later said of the divots Charles made. "When it's the Prince of Wales . . . he's marvelous company."

Charles was similarly impressed, at least by his surroundings. According to Annenberg, who has been knighted by the queen, his royal visitor asked if a "copy" of Sunnylands could be made for Great Windsor Park. "I said that by the time you get through with the zoning commission in your country, I would be long gone."

Charles' latest outing to rub elbows with American tycoons (Armand Hammer's turn, you remember, came last November when his United World Colleges benefited from a $10,000 to $50,000-a-couple dinner in Palm Beach) begins in Texas where he will visit Feb. 17-21.

He'll fly to California after helping Texas celebrate its 150th anniversary and bestowing the Winston Churchill Foundation award on electronics magnate Ross Perot.

Princess Diana will not accompany Charles, according to Annenberg.

"She wants to be with the children," he said. "You can't blame her."

Some of the biggest names of French Impressionism will be on the walls of the National Gallery of Art starting Jan. 17, and some of the same names will be among the black-tie crowd celebrating the opening at a Jan. 15 gala. AT&T, the latest corporate underwriter of a major NGA exhibition, is bringing not only "The New Painting: Impressionism 1874-1886," but also some of the masters' heirs.

Here for the festivities, which will include a reception given by French Ambassador Emanuel de Margerie, will be Minnie Cassatt Hickman, great-grandniece of Mary Cassatt; Jean Marie Toulgouat, great-grandson of Claude Monet; Sophie Renoir, great-granddaughter of Auguste Renoir; Francoise Cachin, granddaughter of Paul Signac; and Madame Durand-Ruel, great-granddaughter of Paul Durand-Ruel, the earliest patron of the Impressionists.

The Century Plaza Hotel in Los Angeles came up with the bright red poinsettia plant but it was Mark Weinberg, assistant White House press secretary, who chose the two photographs to put on the credenza behind President Reagan for his videotaped New Year's Day greeting to the Soviet Union.

Contrary to published reports, Weinberg said there was no intention of recreating the Oval Office in the hotel's Cypress Room. Weinberg said he chose the photograph of Nancy Reagan and the one of the Reagan family, which was taken on the president's second inaugural and included everybody except son-in-law Paul Grilley, because he felt they best reflected the president's preferences.

"He just wouldn't have been without pictures of his family. He has a collection of them in all his studies. I took the liberty of deciding which ones the president would have wanted," said Weinberg, who also provided the frames since he feared the president's might be damaged on the trip west.