G5 wifi

Joining it to the 2.4GHz radio frequency should allow it to stay in communication over a larger area. You might need to separate the 2.4GHz from the 5GHz with a different SSID than the 5GHz radios. You need to also make sure the authentication for the 2.4GHz is the same for what the Roomba is capable of. If the Roomba only supports WPA or WPA2 authentication then make sure both are configured on the SSID for the 2.4GHz frequency. 

if you have the Arcadyan gateway then you will have to use the mobile application to manage it. There should be an option to establish “Separate Networks”. That will allow the 2.4GHz and 5GHz radios to be on different SSIDs. Once that is done then you can join the Roomba to the SSID for the 2.4GHz network. It is pretty much the same as joining any other client to the WI-FI at that point.  If you have a printer that does not play well on the 5GHz then it can also be joined on the 2.4GHz radio and the other SSID. So, in effect you will have two WI-FI networks each with different SSIDs. All clients will join the same wireless ethernet segment so depending upon the client capabilities you select which SSID to join it to the network.