Users assigned tasks in the workflow can continue to approve or reject them even after their roles are removed.

Issue

Users assigned tasks in the workflow can continue to approve or reject tasks even if the corresponding role is removed before the task is approved or rejected.

This behavior is a specification.
Workflow assignments specify procedures or processes to be performed and are not intended to control permissions.
When creating a workflow process, assignment rules are defined based on users or roles.
However, this works only as a task assignment rule and is not treated as an operating authority.If a user's role is deleted after a workflow task is assigned, the user can still continue to perform tasks such as approve or reject.