You're unable to delete an existing roaming profile manually or through a security GPO while the DAgent service is running.
In order to report user information, the DAgent service registers the notification service SERVICE_ACCEPT_SESSIONCHANGE. This is not processed properly by the DAgent on Citrix and Windows Terminal Servers. By preventing the DAgent from registering the ACCEPT_SESSIONCHANGE notification service, the profile is then able to be deleted.
This behavior has been corrected in Deployment Solution 6.9.490 (SP5):
Deployment Solution 6.9 SP3 and SP4 (builds 6.9.430 - 6.9.453)
DAgent (builds 6.9.430 - 6.9.453)