Two types of issues are frequently reported when users are trying to edit roles and are a result of the following two permission problems:
1) You have fewer permissions than the role. You cannot edit the role if you have less permissions than the role, e.g. if you don't have permissions to the Config admin module, you cannot edit a role with access to Config admin. So if you, as an administrator was not given a specific permission that was given to a role, you won't be able to edit it anymore.
2) The role has been shared to groups that you don't have access to. If a role has been shared to a branch in the organisation hierarchy that you are not allowed to access, you can no longer edit the role as it will affect a group that you do not have access to. You can see if this is a problem by looking at the available groups in the organisation setting when editing a role. If the number of available groups is more than what you can see in your organisation tree selection, it means the role has been shared to another group that you do not have access to.
Prevent this by not sharing roles across multiple regions or dealers.