Hi,
I am a Unix / Linux Systems Administrator with over 25 years experience in the IT field.
it is a pity that you are having so much trouble getting a freelancer to make this work.
I have just finished a project with an installation and configuration of roundcube.
Can I ask, what hosting provider you use, as this will depend if the password module will work.
the password plugin has a few drivers, for different providers, with cpanel being one of them, this is the most common hosting platform, but not the only one.
Please feel free to contact me, hereon freelancer to discuss your problem in greater depth.
Regards,
Stephen.
(Australian)