So much for a secret ballot. Last’s year’s “Erin Brockovich” Best Actress Oscar winner Julia Roberts is putting her X next to Denzel Washington’s name on her Academy Award voting sheet. Washington, 47, is in the running for Best Actor for his role as a cop gone wrong in “Training Day.” “He should be on his third Oscar by now, and that might not be enough,” Roberts raved in the current Newsweek magazine in a profile of Washington. The two starred together in 1993’s “The Pelican Brief,” and Roberts, 34, considers him “the best actor of this generation, hands down . . . I cannot absorb living in a world where I have an Oscar for Best Actress, and Denzel doesn’t have one for Best Actor.” Washington has won before, for the 1989 Civil War story “Glory” — though that was for Best Supporting Actor. (In the 73 years since the Academy of Motion Picture Arts and Sciences began dispensing Oscars, five African- American actors and actresses have won for supporting roles and only Sidney Poitier has received a Best Actor Academy Award, for 1963’s Lilies of the Field.”) This year’s Oscar telecast takes place March 24, and Washington’s competition is Russell Crowe in “A Beautiful Mind,” Sean Penn in “I Am Sam,” Will Smith in “Ali” and Tom Wilkinson in “In the Bedroom.” No word on Julia’s choice for Best Actress.