AFAIK the Roaming is achieved on non Motorola DMR radios by scanning TG8 on all the repeaters in your local area/region, setting the call back channel to 'Last Landed' and setting the 'resume scan' for a fairly short time. In action your radio will stop on an active channel, if you wish to talk you TX and you will talk on the last landed (last active) channel, if you loose coverage on RX the radio will scan and stop on the first active repeater with TG8 in the scan list. The only real drawback is to initiate a call you might need to manualy select a repeater channel (Zone) in the scan list.
Connect Systems CS750 and CS800, Hytera PD-365, Motorola DP4600
Raspberry Pi 2 and DV4Mini HotSpot
AOR AR-DV1 Digital Voice Receiver / eSPYonARD
WS1088 / TRX-1 / Whistler Q / UBCD3600XLT