48 is a virtual network (MVNO: http://en.wikipedia.org/wiki/Mobile_virtual_network_operator) operating on the Three network so some phones/operating systems think you're roaming even when you're on the home network. This is not a problem and does not incur any costs or otherwise affect service. Some phones have an option to enable "National data roaming" which gets rid of the "R" but if your's doesn't then just ignore it.
Do you have a data allowance as part of your membership or a data add-on?
Did you configure your internet/APN settings?
http://community.48months.ie/t5/Need-Help/Internet/m-p/34493#M12560
Hope this helps.
