Historically in mojoPortal, when assign a role to a user, that user would have to sign out of the site and back in before he or she would have the new access. Joe added code so that it would automatically update the user's role cookie if the user's roles had changed.
To see the full list of the code and scripts that were changed for this, take a look back through the source repository to changeset 3541 on 1/6/12. The description is: "implemented automatic updating of the role cookie if a user's roles changed"
I hope that helps,
Jamie