The White House has yet to announce nominees to replace the two executives.
Roche and Sambur have been under scrutiny for their role in the Air Force's controversial $23 billion plan to lease tanker aircraft from Boeing. Congress has put that deal on hold pending several ongoing investigations.
The two Air Force officials have struggled to preserve the integrity of the service's procurement system in the wake of the scandal surrounding the Air Force's No. 2 contracting official, Darleen Druyun. The Defense Department is reviewing all contracts Druyun oversaw at the Pentagon after she pleaded guilty in federal court to ethics violations for favoring Boeing in contract talks.
Roche, a Navy veteran who previously was a top executive at Northrop Grumman, was tapped by President Bush in 2003 to serve as Army secretary, but withdrew earlier this year after Sen. John McCain, R-Ariz., sharply opposed his nomination. McCain has harshly criticized both Roche and Sambur for promoting the tanker lease deal, which he views as a congressional handout to Boeing.
The Defense Department's inspector general is investigating e-mails that Roche exchanged with Office of Management and Budget National Security Chief Robin Cleveland. In the messages, which made reference to the tanker deal, Roche offered to help Cleveland's brother seek employment with Northrop Grumman. Roche has said the e-mails consisted of lighthearted banter between two longtime friends, and that Roche's brother never got a job.
Sambur, also a former defense industry executive, had been under investigation for his role in the tanker deal, but was cleared of any wrongdoing.