This guy asks about archival - https://superuser.com/questions/374609/what-medium-should-be-used-for-long-term-high-volume-data-storage-archival

They say to buy a 30TB LTO-8 tape cartridge for $79 - https://www.networkworld.com/article/3638116/why-aren-t-optical-disks-the-top-choice-for-archive-storage.html

ROMs would be useful for storing lots of data for long periods of time without corruption or freeing up space on your SSD for more hot data, that could be automated. They should be cheap and compact. These are useful properties.