By Stephen M. Silverman
June 19, 1998 12:00 AM

Rosie O’Donnell has been called the most powerful critic on Broadway. When she touts a show on her TV chat hour, the box office booms. But now Rosie is putting herself where her mouth is. On yesterday’s “Rosie O’Donnell Show,” the star, 38, announced that she will take over a leading role in the relatively new (and critically lambasted) Broadway musical “Seussical” and will play the role of the Cat in the Hat while the actor currently in the role takes a vacation. Rosie’s appearance in the show, which will be from Jan. 16 to Feb. 10, will be during what is traditionally the slowest period for Broadway, when many shows teetering on the box-office edge simply pull down the curtain for good. Instead, theater observers estimated for The New York Times, the “Seussical” box office is expected to triple. “I love the show, and I thought the critics did it a disservice with their reviews,” Rosie, who said she will donate her salary to charity, told The Times. “As a parent and a mom and someone who loves the theater, this is one show that should survive.” It might also help that the show’s producers, Barry and Fran Weissler, cast Rosie as Rizzo in a 1994 revival of “Grease” during a slack period in her career.