Help & troubleshooting for network issues, including connecting your device to your home Wi-Fi network, connecting to public networks, troubleshooting wireless issues & ethernet connections, and optimizing streaming performance.
Easiest method is to access your router's admin page and look for it under Wireless Settings. (normally an option to Unmask/Unhide if you are seeing hidden in router settings). You can also change your password from same section. Press Save, Apply Settings, and restart router to take affect.
The other option is to factory reset the router and use the default setups/password normally printed on bottom or side of router, but will have to setup your network again from a default state.
Another method is to see if your mobile phone or laptop/computer saved the password under its Network login settings and provides an option to unmask.
Unfortunately, no shortcut within the Roku itself to show or unmask the previously used network password.
But if you have access to a laptop or phone and you have used them on the network before, you can use various methods to recover a lost wifi password. You just can't use the Roku directly to accomplish this unmasking.