RISC OS 3.7 and 4.39 has 4MB, RISC OS 5.xx 5MB unsqueezed ROMs. So it is not relevant. Have 240MB free on my Classic Pandora after the desktop ist working. Is my standard config. AppDock, Fat32FS and other additional stuff is loaded.
Update and try new ROMs are easier...
My Risc PC has 4.39...