Hello,
Roundcube does support such feature, although it's not very explicit about it.
First thing you want to do is to create a folder for your templates. It must be a different folder than drafts, due to drafts folder behavior.
Now, assuming you have your templates folder, start new message, put there what your template should contain and select "Save this draft". Then, move that draft to your templates folder (otherwise if you send out that message, it will be automatically deleted from Drafts).
Now, with your message saved in Templates it's time for the easy bit.
When you want to send a message from a template, simply open Templates folder, select the message you want to use and click "More actions..." (cog icon) and "Edit as new".
I know it's not perfect, but that's the only way I've found to approach this matter. And from what I read recently, Roundcube developers don't intend to implement better templates handling, saying that the "Edit as new" option should suffice.
Hope this answers your question.
Kind regards,
Arek
