To update the users' roles on Deskera Mobile App, go to the Users under the Organization Administration.

In the user's display page, you should be able to view all the users you have added to the organization previously. Tap on the users you wish to update or change the roles. This will open the screen as shown below.

Edit the user's details and role.
 Update the user's new role.

On the editing user's page, you can edit the user's name and last name only. You are not able to update the email address. Next, you can also change the user's role accordingly and click on the Tick icon to Save.

Do note that you cannot remove or delete the users on Deskera Mobile App.