First thing came to my mind. I don't think there would be any difference between local and roaming customers if the operator is same.
For instance: if we have two users of Vodafone. One is in roaming and other is a local customer. It depicts the same meaning for radio like two local customers are there. BTS will see the Power, Periodic reports and all things which it usually does in normal scenarios. There will not be any difference for assigning the resources to them.
According to me there is not as such technical segregation until and unless If i am not subscribed for any kind of special subscriptions.
If the users is latched on other Operators Network at roaming period then it might depends upon their business standards. How they have made the deal. In this case they can set the priorities of the User. High Priority and low Priority.
Note: I have not considered here International Roaming.
In LTE there is concept of this which selects the promised bit rate. I suggest you below link.