It looks like may be the version of TinyMCE used on that demo page you linked to is 4.7.2 though I see that was only released yesterday so may be when you tried it it had 4.7.1.
The last version of Roundcube shipped with version 4.5.8. You say you have updated that to 4.7.1? There may be other things you need to update in Roundcube to make it compatible with the new version, probably in editor.js, don't ask me what they are I do not follow TinyMCE dev.
Finally you said your configuration is standard but the screenshot you posted looks nothing like the editor in Roundcube. You have a menu bar, Roundcube does not have that and the toolbar looks different too.
I'm not sure what you are doing exactly but it still does not seem like a Roundcube issue to me.