using role in js
One answer
I don't know any ways to retrieve the process roles (project level) for a user given the limitation of the JavaScript extension (it's really meant for dealing with the current work item only).
Comments
I second that and would also like to state that objects like the one Don mentions above, are only available in the RTC Web UI. They are not available in the JS running in the Eclipse client.
You can use Java to create attribute customizations to access this in Eclipse and in the Web UI. See https://rsjazz.wordpress.com/2013/06/26/attribute-customization-java-based-value-providers-conditions-and-validators/ and https://rsjazz.wordpress.com/2015/08/07/a-custom-condition-to-make-attributes-required-or-read-only-by-role-version-2/ for example code.
You might be better off using a follow up action, because that only needs to be deployed on the server. See https://rsjazz.wordpress.com/2015/09/30/learning-to-fly-getting-started-with-the-rtc-java-apis/ for more information about your options.