Hello Annette, I can't speak to the Landmark side since the only Landmark application we have is IPA. However, when I was researching how to remove and/or change LSF security (ie Roles and Groups) for employees with position changes via IPA, support provided the attached uber simple flow as an example. Basically, use the Resource Update node to reset the user's Roles and Groups to a more limited list - or removed them all together. As a disclaimer, I haven't actually gotten around to adding this logic to our workflows, but it would seem to be a workable solution.
Just thought I'd share in case it may be helpful to anyone.