You can view and edit worktime role members in the action menu under worktime roles.
Once you've selected the right worktime role, choose "worktime role members" as action.
A list of all users in the service is now displayed. The members of the selected worktime role are marked by blue box in front of the name.
If you want to add members to selected worktime role, you can tick the box in front of their name and then click 'Save' at the bottom. Now user has been transferred from one worktime role to another.