Roundcube is a piece of software not a service provider. The only people who can tell how/why the canned responses were deleted is your hosting provider. You have a pretty narrow window when it happened so they should be able to find something in their logs and hopefully they have backups and put them back for you.
From your description it sounds like you lost your settings as well. That's a clue. Just a guess but one possibility is that a duplicate userid has somehow been created in the Roundcube db and this new id does not have all your settings, canned response, etc. But again only someone with access to the database behind the Roundcube installation you are using would be able to look into that.