You do NOT own the intellectual material and have NOT bought a liscence to make copies.
Alot of countries have a law called fair usage or something along these words, which let the user make a copy of his legally bought product. This also extends to for example using hack to defy encryption to be able to lets say play a dvd on linux.
If you chuck the original media (i.e. the original discs) I believe you are then throwing away your liscence as well. You cannot legally retain and use copies or keep a backup.
I think the license is basically the roms when it comes to workbench anyways. The kickstart roms are a part of the OS.