I don't understand how the Email Template work. There seem to be two system. How to use email template?
Email template is separate from Roundcube email.
Roundcube should have access to Email Template(?). Send a email from Record view (Contact/Account/etc)

^ This option is what I see in Roundcube email template.

^ No idea how to activate these email template in the Email Template module.
This is the same email template list, but the one you can see in Roundcube only displays the templates whose type is "Message", and the list you can see in the Email Templates module displays all types of templates - "Message" and "Record".
what is the difference between "Message" and "Record" email template type