@WilsonPhillips and @all
It’s up to you.
For ROME (rolling branch) we’ll mainly need test the major upgrades, and the existing packages;
Yes you can enable the /testing repo on ROME.
It’s as risky as if you run cooker. Testing repo packages are backports from cooker so by design ‘untested yet’ in ROME system 
The workflow is: the new builds go first in /testing and after a while we publish them in main repo. Often we move the deemed safe packages in main straight away.
Cooker is way more exciting because of new builds every day. That probably requires an advanced user who can sort the issues if any and/or can recognize and avoid them and promptly report, better if in the cooker channel.