Use mkcd as bjverzal mentioned. There is an option (-I) that will output the iso images as files named cd_image_123456.vol1...vol2...vol3, etc. instead of burning them to the writer. (which is a good thing, since I guess there isn't one attached to the RISC box). Refer to the man pages for mkcd if you are using the command line. If you prefer SMIT, use the fastpath 'smitty mkcd'.
Then you can transfer them to the PC (FTP?, SAMBA share?) and burn them with whatever software you are using. I've booted from and restored from images created this way a few times without any problems. BTW, if you use FTP to transfer the images, make sure you transfer them as BINARY and not ASCII. Good Luck!