Hello,
You may see that sentence here in this topic: ROME major upgrade expected
Usually:
“ROME users attention please: The process to copy cooker repositories to rolling (ROME) started. […] We’ll keep you informed when it will be the time to perform distro-sync again”
Followed by (after a few time):
“Process finished. It should now be safe to distro-sync ROME system”
often also providing reminds, warnings and/or workarounds if any need.
I’m going to publish such an advice right now in facts.
ROME users should bookmark and subscribe notifications if not done already to that topic.
Besides that, you can upgrade system any time (except the brief window time between the 2 notices).