Hey @Joe_W,

Great Question! There are a few things that can cause the behavior, and adding them to the guest network basically takes all of them out of the equation. A few of which can be found below:

- Your Guest Network can be limited to 2.4GHz, preventing devices from having problems with the 5GHz network.

- The Guest Network is isolated from other devices on your network, avoiding any conflicts with other devices or existing network traffic.

- Devices on the Guest Network do not roam as aggressively and lack many of the features providing a 'seamless' roaming experience.

- The Guest Network has a different SSID; removing the possibility of misconfigured connections or  settings from previous networks of the same name from interfering

I would recommend adding the Rokus to the main network and trying the following settings for your network and in the client settings: Disable Beamforming, Disable Mesh Technology, and Consider Disabling Fast Roaming for the main network. I believe that your model will have all three of these. 

If the devices do not connect to the network at all, you may need to change the security/encryption type of your Wi-Fi to WPA /WPA2

You could also use try the "Client Signal Preference" to try and force the Roku to connect to the closest node, or to force the Roku to connect using a specific frequency.