Ohhh wait a minute... I think I slightly misunderstood what you said by "Users are not showing"
I thought you were talking about that they won't show up when adding them as Members of a Role in the Admin Portal. But it seems that what you meant is that, even added to a Role, they are not showing into the Users list in the Admin Protal, right?
In that case explanation is rather simple. When you add the User to a Role, that means he is now entitled to access your Office 365 App, for which there is provisioning enabled (syncing AD Users into your Office 365 tenant).
Fact is an AD User will only appears into the Users list when they are provisioned by Centrify, i.e. once they logged in at least once to the User portal or to Office 365 (and then redirected to the Centrify Cloud). When they log in the first time this will trigger the provisioning and then they will appear in the User list. Provisioning for Apps is also triggered by default every night, this would also make the missing Users appear in the list. So whatever come first, Users loging in or the nighlty provisioning job, will add the AD User to the known Users list.
Hope that make sense.
Fab