You can easily reset the root password on linux-based VMWare appliances through the boot loader. For this to work, you need access to the console of the appliance (i.e. through vSphere (Web) Client), and needs to be performed during offline hours as the appliance has to be rebooted.

Reboot the appliance, and as soon as you see the GRUB boot loader, halt the automatic boot timer by hitting any key (I usually move the selection using the arrows).

Select the first entry, and press e, allowing you to type in some text. At the end of the line that starts with kernel, add the following text:

init=/bin/bash

Do not remove any other text. Then press Enter to confirm.

Press b to continue the boot  ...