It's not possible with one or two caveats: if you can remember the SSID/network name and password of the Wi-Fi network the TV was last connected to as long as you haven't performed a factory reset. Or, if the TV has an Ethernet jack on the back and you can connect it to your router then it may connect to your network and you may be able to use the app to connect it to Wi-Fi.
Otherwise you need a physical remote. Many universal remotes support Roku TVs or you can get a Roku Voice Remote at many big box stores that will work with your TV once it's paired.
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