Roku also allows for hidden private channels, which are not shown in the store. These could be channels in beta, or they could be unofficial channels that let you access podcasts, games or other streams. For example, Nowhere TV offers a ton of podcasts and free videos from around the web, TwitchTV brings Twitch back to Roku (after it was removed from the official store last year), and the Redbox Beta channel gets you the latest features before they're released to the main Redbox channel. The best way to find private channels is to browse an unofficial database like RokuGuide.com. If you see a channel you want, select it, then click Add Channel and RokuGuide will redirect you to Roku's website and install the channel.
Cast from other devices to your TV
If you find navigating Roku's interface too cumbersome, you can cast certain videos from your phone instead, like Google's Chromecast.
Both the Netflix and YouTube Roku apps support an open protocol called DIAL that lets you cast videos from your phone or tablet. Just open the Netflix or YouTube app on your phone and tap the Cast button that appears; your Roku device should appear in a list of available devices, and you can throw videos from your phone to your TV. Sadly, this is not supported by other apps, which tend to use Chromecast's proprietary protocol instead.
If the Roku channel in question doesn't support DIAL -- or if you want to cast media that doesn't have an associated Roku channel to begin with -- you can also mirror your Windows PC or Android device's screen. This should be enabled by default, but you can double-check by going to Settings > System > Screen Mirroring on your Roku and making sure it is set to Prompt. (Note: This feature is not available on the Roku Express.)
To mirror the screen of a computer running Windows 8.1 or above, head to Settings > Devices > Add Bluetooth or Other Device. Select Wireless Display or Dock. To mirror your Android phone (running Android 4.4.2 or higher), head to Settings > Display > Cast Screen. Tap the menu button in the upper right-hand corner and check Enable Wireless Display. From there, you can go back to Settings and choose Cast Screen. It's also called different things on different Android phones, so if you can't find it, check out this Roku support article for more information.
Note that Miracast, the protocol used by Screen Mirroring, is only supported on certain laptops and phones, so it may not work for you. If you're lucky, though, you should be able to throw just about anything to your TV using this feature. Video quality may not be quite as good as playing it directly from a Roku channel, but it's better than nothing.