For some devices, such as iPhones, it is not necessary to have roaming turned on. For other devices, roaming will need to be turned on to use the GigSky service. However, turning roaming on may inadvertently turn roaming on for your domestic service and you may incur roaming charges from your domestic service provider.
If you can't be sure that roaming is off for your domestic service when traveling, turn off or remove your domestic carrier's SIM/eSIM.