Does tube rolling with regard to CDP mean...

Bringing more color into the sound reproduction? If that is the case then tube rolling would be: changing tubes until you find the right coloration. But isn't it true that the live sound is what we are after? In that case tube rolling should mean: changing of tubes until the sound resembles live music.

Tube rolling can be much more than coloration.. detail, soundstage, dynamics, presatation and yes color (warmth brightness etc)
In many pieces of equipment tube rolling can max out sound quality improve listenability and reduce fatigue.
Yes but recorded sound is not live. Therefore you roll tubes to find the sound you think sounds live. The equipment manufacturer may have used a tube that you think sounds live in which case no need. In general Ihave found that I get the most pleasing sound if I roll tubes. On occasion I don't, but it's the exception not the rule.
I rolled the stock 6922's in the Cayin to Sovtek's and like the sound slightly better. IOW worth the $150/quad investment. There's others that might be even better for more $, but don't feel the need to invest at this time. maybe in 2 yrs from now I'll try another set.
hi arthur:

live sound is correct instrumental timbre. when you listen to a musician play an instrument in a "room" or "hall" that is reasonably acoustically benign, you hear live sound.

how well we can store in our brain "live sound" and make meaningful comparisons with the sound of a stereo system is another consideration.

as to tube rolling, very often replacing the tubes has a minimal affect on the sound of a stereo system. i would say change the tubes as long as you create a presentation you prefer to what you hear with the stock tubes.
I am sorry but an instrument played in a "room" versus a "hall" will sound very different. That was my point. Mechans got it right - "live" sound is what we "think" is live sound and your live sound won't be like my live sound and the live sound of a band playing outside won't be the live sound of that band played on a stereo and a classical symphony in a concert hall's live sound won't be that live in a stereo room either. Live sound won't ever have an absolute reference, I assure you.

Just find what you "think" is live and all is well. Otherwise you will never be satisfied in this hobby and you will spend the rest of your days searching for the "best" stereo in frustration. Just read many of the posts people have here in this forum if you want examples.