LanMan98

LanMan98 is a CIFS client for RISC OS. In short, it enables RISC OS machines to access shared storage across a network, and also (with suitable printer drivers) to print to network printers.

This means that your RISC OS machine can transparently access drives shared on PCs, Macs(*), Linux and other operating systems, including dedicated Network Attached Storage (NAS) devices.

(* Some versions of Mac OS may require additional software on their end.)