Change WordPress user roles and capabilities › Forums › Restrict or Permit access inside WordPress – how to › Restrict Access to Custom Taxonomies › Reply To: Restrict Access to Custom Taxonomies
Currently I can not recommend another workaround then that you use already.
But it’s a good point to extend User Role Editor Pro functionality. I will think on it. May be something similar to the “force custom taxonomies to use own capabilities” option will be possible to add. I will post here as I will find a decision.