That sounds like a scam message. Roku devices themselves do not have a subscription, although certain channels do. Unless someone has hacked into your Roku user account, there's no way someone can do anything to disable your Roku devices. As a precaution, you should log into your Roku user account (https://my.roku.com) and change your password.
Dan Roku Stick (3600), 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.