A Washingtonian traveling in the Bahamas last week paused to sign the register at the expensive Greycliff restaurant in Nassau when he noticed a familiar name in the book. On Jan. 3, the name of fugitive financier Robert Vesco was penned in, giving his address as Havana, Cuba, and commenting: "fabulous and discreet" . . .

Howard Cosell, who was in town last night to get a Washington Journalism Review award, will guest-host one of the February editions of NBC's "Saturday Night Live." Executive producer Dick Ebersol said yesterday he has been trying to get the last angry man for years and "finally, he said yes," though the date still has to be firmed up . . .

The Radio City Rockettes, who have been protesting being forced out of Radio City Music Hall for the summer by Walt Disney Productions, were offered a compromise of 10 weeks' work this summer at Disney World. Late yesterday, they turned down the deal. . .

Jay Rockefeller delayed his swearing-in as a United States senator for 12 days so he could complete his term as governor of West Virginia. By the time he was sworn in Tuesday, he achieved the unhappy distinction of being 100th in seniority, right at the very bottom of Senate assignments and privileges . . .

When Ohio high school basketball star Jay Burston broke the state's all-time scoring career record, the John Glenn High School star from New Concord, Ohio, was playing a game in the John Glenn Gymnasium of Muskingum College. And in the audience was Sen. John Glenn, who had attended the high school when it had a different name and had played basketball there. "I'm embarrassed," the former astronaut said. "He scored more points in four short quarters than I scored in four long years" . . .