Setup SSD storage, access via Roku

Noobie here. I am trying to set up a Plex-at-home solution to my large DVD collection. I have a Roku Ultra and I would like to convert my DVD collection to files stored on a SSD.
Is it practical, feasible or smart to put my movies on a 1TB SSD attached to my wireless router (via USB) and have the Roku access those files via Plex?
Some discussions suggest a NAS device, others an old computer. I am happy manipulating Plex via my linux laptop and using the Roku for playback. I have watched several youtubes which are mostly depressing and I am reading articles here on plex which are chipping away at my ignorance but I am still hesitant about what I’m doing because mistakes can be costly.

If you are running your Plex server on a computer anyway, it doesn’t make sense to plug the media hard drive into your router. Plug it into the machine that runs Plex server.
Running Plex server directly on a router device is not practical.
Plex server has to be running whenever you want to use your media.

Start with a computer that you already have.

Side note: it doesn’t make much sense to store media on a costly SSD. You won’t need its speed of access nor its bandwidth for this use case. A regular hard drive will do just fine and will provide much more storage capacity per buck.
You can however use an SSD for Plex’s metadata storage (the so-called plex data folder). Which, again should be on, or even better inside the server machine.

Otto, thanks for the insights, I had not given them much thought. And now, having fiddled a bit with my Roku ultra I’ve discovered that it has a usb port for attaching a storage unit to be accessed by Roku media player. I think that is all I need to replay my movies.
Still, this problem and your response has provoked me to think a little harder. Thanks.