Worker roles are designed to control the permissions and configuration a worker has when they are logged in to the system. Although they may also represent the job role that worker has, they are not designed for this purpose and should be represented elsewhere. They provide an audit to show what permissions a worker had on which dates and to control what they were able to do as a result.
Where worker roles had been changed retrospectively, the audit is then incorrect, as it shows the worker having permissions (or not) at a point in time incorrectly. For example:
Worker A is a System Administrator. They change job on 5th January and become a Social Worker, but their worker role in Mosaic is not updated until 10th January. On 6th January they deleted a workstep. On 10th January, their worker role is updated to Social Worker with a start date of 5th January, where they do not have permission to delete a workstep. This invalidates the audit trail, as it then looks like they were able to delete a workstep on 6th January without having that permission.
It is important to see this as just a change of permissions and it should not be happening retrospectively, as its impossible to give someone permissions in the past. We understand that the fact that these roles are often named after the jobs to help identify the correct one leads you to want to update it to fit the job start date, but this is not the correct use of this functionality.
This validation is correct and will only stop you from updating the role to dates when that worker was active in Mosaic. They were active under the previous permission set (worker role) and so should remain as it is for a correct audit.
We do not support these changes being made in the Admin Tool to get around the validation, this will mean we continue to see problems where worker permissions are artificially updated. All updates should be made in Mosaic, and the validation will ensure that these continue to ensure there is an accurate audit of the permissions a worker held at any one time. Recording the dates a worker has had a job role should happen elsewhere and is not the intention of this functionality.