I wanted to add a reference to this plug-in to this thread too:
https://moodle.org/plugins/view.php?plugin=local_cohortrole
So, if you are using LADP to create your users, you can also create user groups from your active directory. Those groups can create cohorts in your moodle site. If you also need a group of users to be assigned a role, the plugin above should assist with that part of the task.
Disclaimer: I have not used this plug-in, but have been scouring the forums for so long that I thought it would be important to share this discovery. I hope it works!