The rumors are apparently true. Rove is cooperating with the Fitzgerald investigation, and pointing investigators to the Cheney office. It was Rove, reports say, who informed Fitzgerald about the "missing" emails from the VP’s office. From The Washington Note:
According to several Pentagon sources close to Rove and others familiar with the inquiry, Bush’s senior adviser tipped off Special Prosecutor Patrick Fitzgerald to information that led to the recent "discovery" of 250 pages of missing email from the office of Vice President Dick Cheney.
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According to one source close to the case, Rove is providing information on deleted emails, erased hard drives and other types of obstruction by staff and other officials in the Vice President’s office. Pentagon sources close to Rove confirmed this account.
None would name the staffers and/or officials whom Rove is providing information about. They did, however, explain that the White House computer system has "real time backup" servers and that while emails were deleted from computers, they were still retrievable from the backup system. By providing the dates and recipient information of the deleted emails, sources say, Rove was able to chart a path for Fitzgerald directly into the office of the Vice President.