A Reddit user seems to have observed Starlink doing true roaming today:
https://www.reddit.com/r/Starlink/comments/ssj464/starlink_roaming_is_working/

It appears that there is now a system in place for Starlink to re-connect
even if you are outside your official service cell. For those of us who
want to use Starlink on vacations or other trips, this is quite the
development.

--Jonathan Bennett