When going to the settings in Roundcube there is a :Filters: setting, clicking it throws an error about not being able to connect to the server. I do not have a plugin installed like manage sieve, so I'm not sure what this "Filters" is supposed to do.
$config['plugins'] = array('archive', 'emoticons', 'help', 'hide_blockquote', 'identity_select', 'markasjunk', 'logon_page', 'logout_redirect', 'message_highlight', 'dovecot_ident', 'listcommands', 'managesieve', 'keyboard_shortcuts', 'customizr', );
If you do not want the filters tab then remove managesieve from your list of plugins.