When creating a new Group Managed Service Account in the Active Roles Web Interface, the search operation on the Membership Policy tab will not return Computer objects. It will only return Users and Groups.
Create and manage Group Managed Service Accounts using the Active Roles Console.
Although this defect is noted under the Resolved Issues section in the Active Roles 7.3.1 release notes, it was only partially resolved. The search operation functions as expected on an existing Group Managed Service Account, but does not return computer objects when creating a new Group Managed Service Account.
Waiting for a fix in a future release of Active Roles.