If the content stored on CDs and DVDs were in a AppleTV-friendly format, you could get away with adding them to iTunes (not copying them to iTunes Music, BTW) and syncing. Repeat for each CD/DVD you have--once the sync is complete.
I think iTunes would keep the link to the file despite the media not being available--it'll have that exclamation mark beside the name. It won't be removed from AppleTV unless you remove it from iTunes.
I have not tested this, but it should work based on my understanding of iTunes and iPod syncing.