I'm not sure what you mean by WiFi/WLAN data roaming. Roaming typically is related to the mobile network, not WiFi. Are you wanting to roam on a network belonging to a carrier other than Vodafone? Does your wireless data plan include roaming?
In a home network in which a wireless router and one or more wireless repeaters are used, the wireless networks of the individual devices overlap. If a smartphone, tablet or other WLAN device in such an environment automatically changes the connection from the weaker to the stronger wireless network, this is referred to as "WLAN roaming".
In several online forums it is suggest to activate WIFI/WLAN Roaming in developer options.