On all our sites we have a pseudo-admin role that can do many of the things an Admin can do, but is still very limited. One of the issues we have run into lately is with the User and Role management. We don't use the core user manager as we don't want the pseudo-admins to have the ability to apply the admin role to themselves or other people. Currently, we use Work Control's User Manager but development and support has been pretty flaky lately.

I was wondering if anyone else uses a similar module or knows of one to allow non-admins to add users/roles (but not have the ability to edit admin users/roles).

Any help would be greatly appreciated!

Right, but if we want them to be able to add users and roles they would need edit access to the module, which means they would be able to apply Admin role to any user, correct? That's why we use a 3rd party module, because that module allows you to filter out roles you don't want them to have access to add/modify.