nexus9 just brought up a good point I neglected to think about.
It has nothing to do with the OS. Whether or not you can boot from a CDROM on a SPARCstation depends upon the Open Boot PROM and NVRAM.
Go into your OBP. To get in, hit 'STOP' + 'A' when it begins the boot, or during the diag routine. At the prompt, type 'probe-scsi'. If you have a CDROM connected, it will show up. Usually as device 6.
I've taken SPARCstation 2s, popped the top and sat a 50 pin SCSI CDROM on top of the hard drive, connected it up and worked from there.