Motorola DMR radios typically have roaming capability. I've recently configured roaming for my XPR-4550 and here's some details on how it works and how to setup. 

Roaming is a feature that can be enabled on a per channel basis in MotoTRBO radios which support it. 

The first step is to setup a "Roam Group". This is very much like scan groups in other DMR radios. 

  • Any member of the Roam Group is considered equivalent and will be evaluated when roaming is enabled.  
  • Roaming is based on the RSSI of each channel (signal strength), so alligator repeaters will skew response. "Gen two" (MotoTRBO 2) radios allow per channel RSSI which can allow individual tuning. 
  • You can set a minimum RSSI for the group below which any channel in the group is not considered usable. I remained with the default, but this is something that can be tuned. 

Once your Roam Group is setup, you then need to apply it to one or more channels. Unlike Scan Groups, if a channel has a Roam Group listed it automatically initiates roaming across the channels in the Roam Group

Because of this automatic aspect it is convenient to setup a zone for roaming. Here's what I do, based on examples I've seen in other codeplugs:

  • Create a zone for roaming. Initially, I created "GA Roam" and "M1 Roam" for the Georgia statewide and Atlanta Metro 1 channels respectively. 
  • Though not necessary, I put all channels in my Roam Group in the zone. 
  • Each channel in the roam group I then set their scan/roam to be the roam group. Again, not necessary, but this allows me to select the most likely channel ("Selected" in Motorola terms), but it will still roam across all channels in the Roam Group whether that channel is in the zone or not. 

To initiate roaming, all you have to do is select one of the channels with that Roam Group set. It's automatic, and you will see (on the 4550) a light start blinking and also a little antenna icon illuminate. 

Again, it's not a requirement to have a separate zone. But because the roaming is set per channel and is automatic, it is convenient to have a way to differentiate channels which trigger roaming vs the same channel not set for roaming. 

Which leads to another nuance- unlike many ham radios, once a channel is copied into a different zone it's settings are unique. So you can have the same channel in one zone with roaming set, and in another zone the same channel without roaming. Where most ham (TYT, CS, etc) CPS's the channel attributes are defined in the channel setting, and apply to any zones which has that channel in it.