How to theme 3rd party modules?
Best answer on how to theme 3rd party modules is always to check their local documentation first, as most of the top-tier modules have very specific hooks, documentation, guidance for how you can theme their results. In the case of the Rate module, check the README.txt file for some guidance on what theme variables are able to be used in your node templates.

It looks like the best answer would then be to make a copy of the rate template into your theme folder and add your styling there:

* rate-widget.tpl.php
  This is the default template for all custom widgets.
* rate-widget--NAME.tpl.php
  This is a widget specific template. Use the machine name for NAME. Replace
  underscores by dashes in this name. This template is only available for custom
  widgets.


This does depend on exactly what it is your trying to theme in the emotion widget.