The name of free-lance journalist Selwa "Lucky" Roosevelt has moved to the top of the list in the ongoing guessing game about who will become the next U.S. chief of protocol.

The socially prominent Roosevelt has publicly defended Nancy Reagan's life style. She is married to Teddy Roosevelt's grandson, Archibald B. Roosevelt Jr., who is an official here with Chase Manhattan Bank. She confirmed yesterday that she is in the running.

"All I've been told is that I'm under consideration," said Roosevelt, 53, known to be a favorite of both First Lady Nancy Reagan and Michael K. Deaver, the president's deputy chief of staff, who has led the search for a successor to Leonore Annenberg, who resigned on Jan. 1.

Last night, Deaver was not available for comment. At the State Department, however, acting chief Tom Nassif said he, too, had heard the rumor.

"I think we're very, very fortunate to have someone like her being considered," said Nassif.

A Tennessean who moved to Washington in 1950 after her marriage, Roosevelt was among the Washington establishment befriending Nancy Reagan shortly after the Reagans moved into the White House. Last fall, as criticism mounted of the first lady's life style, journalist Roosevelt came to her defense with a rebuttal written for The Washington Post op-ed page. Mrs. Reagan later wrote her a note of thanks.