If you subscribe to anything though Roku, you can find that information in your Roku user account (https:/my.roku.com). If it's not listed there, then you are not subscribed through Roku.
Exactly what subscription are you referring to? There is no subscription to the Roku itself. You don't have to "subscribe" to anything to use a Roku device. Yes, there are providers that require a subscription, but that's not the Roku itself.
Dan Ultra (4640), Ultra (4670), Ultra (4800), Premiere (3920), Insignia 720p Roku TV, Sharp 4K Roku TV, Nvidia Shield, Windows 10 Pro x64 running Serviio and Plex on a wired Gigabit network.