There are five bearings in a rohloff, three at the drive end and two at the non drive side. The two large main hub bearings are 47mm od x 35mm id x 7mm wide. The two smaller 28mm x 12mm x8mm are fitted in the driver itself and the smaller 22mm x 9mm x 7mm is fitted to the shifting shaft. The two larger bearings (47mm) use the hub oil as lubricant as they are open sided, the two driver bearings are sealed and use the grease within them to lubricate along with the shifting shaft bearing which is also sealed.
They are certainly not superior bearings and will not withstand any water within the hub which has caused problems for some people, due to the fact that the oil seals on the outer of the hub have let water in and corroded the bearings.
All of the bearings can be replaced by the user if you have the knowledge and tools.
47mm bearing code - SKF # 61807
22mm bearing code -This is a custom bearing only, I can supply, if you have difficulty getting one (which you will)
28mm bearing code - SKF # 6001 2RSH
The bearings fitted are of standard supply and are available from most bearing supplies although the 47mm ones are not listed at some suppliers.