Attaining Six Sigma is a team effort. An organization who wants to attain Six Sigma needs a lot of restructuring and change in attitude. It includes building up the following roles to take up the required responsibilities:

Executive Leadership-Includes CEO and other top management team members. They set up the vision of Six Sigma and empower their team mates with the freedom and resources required for the improvements in the process.
Champions- Responsible for the implementation of the process in an integrated manner throughout the organization. They come from Top management.
Master Black Belts-Act as in-house expert coach for the organization. They assist Champions and train Black Belts and Green Belts.
Black Belts-Apply Six Sigma methodology to specific projects. Their focus is on execution of activities for Six Sigma.
Green Belts-These are like the soldiers on the war front who actually implement the planned action.   _{Your Comment}