How can I control access to group-private content based on organic groups roles? I would like my groups to be able to create content that is not only private to a group, but also private to certain roles within the group. For example, a post that is only accessible by members of Group A that also have the "officer" role.

Ideally, I'd be able to make the roles group-specific because different groups should be able to create and assign roles to their members.

How can this be accomplished?
I needed somewhat similar functionality for a drupal 6 site and gave up on using OG for this.
Instead I made a vocabulary that defined my groups and used tac_lite for setting access.
The setup is being ported to drupal 7 right now, and I haven't had any problems implementing the same functionality in d7 so far. 
Maybe tac_lite is a solution for you? http://drupal.org/project/tac_lite