All three of my Roku boxes stopped working today. I have unplugged them and plugged them back in. The dancing letters show up and then the home screen, but it doesn’t react to the remote when I want to click on a channel. It seems the home screen is frozen. I just purchased these Roku boxes in December.
What model Roku players are they? It sounds like a remote issue, which can sometimes be resolved easily. Most Roku players (except the Stick and Ultra models) come with a simple IR remote. There's nothing to pair, the remote must just have a clear line of sight to the Roku. But if the remote has a voice command button, or a headphone jack, then it's a WiFi Direct remote that must be paired with the player. On rare occasions they might lose their pair, but in my experience it's not been common. If it's WiFi, there's a pair button under the battery case.
If they are IR remotes, first check the batteries and make sure they are good and installed correctly. Some remotes have both batteries pointing the same way, while other remotes have the opposite. Then you can test the IR function by viewing the remote though a digital camera (such as a phone camera) and watch for a flashing light when you press any remote button.
Hopefully someone isn't playing a trick on you and installed the batteries wrong. Seems odd that all three would do it at the same time.
Dan Roku Stick (3600), Ultra (4640), Ultra (4670), 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.