how to add a role option in the CreateUserWizard with a checkboxlist

in my CreateUserWizard I have a checkboxlist which is bond on page_load with all existing roles. I want the admin to be able to assign multiple roles to user inside the CreateUserWizardStep. It works fine when edit an existing user. However when add a new user, selected couple of roles in the role checkboxlist, then i try to retrieve the selected roles in the checkboxlist inside RegisterUser_CreatedUser method, nothing is selected.
Any idea why this is happening?

thanks in adavance
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