You can use the Edit IAM Role dialog to edit the description of a IAM Role resource for the target AWS platform.
In the Web Interface toolbar, select the Platforms tab.
Select the platform, then click Edit.
Under Associations, select the IAM Roles tab, then click Edit (or double-click the IAM role) to open the Edit IAM Role dialog.
Modify the Description for the IAM Role resource.
Click Save to update the IAM Role resource.
Click Close to exit the dialog.