Roundcube mail can be setup to automatically insert signatures into your emails. Here is an FAQ / How To doc, so you can set up your signature. This FAQ is also available to download as a PDF Setting-up-signature3s-in-roundcube-mail
Step 1 – Log into web mail then click the settings / options cog
Step 2 – Click on the identities option
Step 3 – Select your identity
Step 4 – Add your signature to the signature text box
Step 5 – Go back to preferences
Step 6 – Click Composing messages.
Step 7 – Set your signature options
Step 8 – Enjoy.