A:Answer It seems the Roku will support 4TB's from an internet search I did however not sure if it'll support more than that. It can't be formatted as exFat. Needs to be formatted with the following: FAT16, FAT32, NTFS, EXT2, EXT3, and HFS+. Also to note, it seems you can't use a portable hard drive. The external hard drive needs to have a power supply because some of the Roku's only support up to certain milliamps.