The RoleId is the InternalId of the role that will be used to log in to NetSuite. Leave empty to use the user's default role.
Together with User, Password, and AccountId this field is used to authenticate to NetSuite. If no RoleId is specified, the user's default role will be used. Otherwise, a RoleId may be obtained by logging into NetSuite, and navigating to the Setup -> Integration -> Web Services Preferences page. Here you can select a different Web Services Default Role as well as obtain the Id, displayed next to the specified role.