I myself did a period of tube rolling with both Vintage and New Valves as well as Russian Equivalent types.
My assessment as a result of demonstration and comparison, has shown, it is quite possible to create a few different end sonics, but if maintaining the perception that the Details, Dynamics and Envelope is being kept to a attractive level. Not all Valves selected that can change the end sound to one that can be lived with are capable of maintaining the above three attractive traits. There are compromises to be made.
The Coherence across the frequencies is a similar decision to be made. Tight Rolled off Bass Notes with a push to project the upper mid's upper high's / Loose Bass which is heading from very precent to overwhelming with the impact of subdued Upper Frequency through to the perception these frequencies are quashed.
Somewhere in this perception of Sounds Produced and their Structure there is a Valve that one individual will love or loath.
I chose the Ken Rad Black VT231 as the Valve to offer a honest Roll of in the Bass and allow the Mid's and Upper frequencies to be balanced in the frequency range. Added to this, the Details, Dynamics and Envelope are in my view a structure to the sound that is present to a very attractive level.
Tube Rolling can offer an immediate noticeable change to an end sound, as Valve exchanges occur. It is this sound difference only that is recognised and the other important qualities of how the end sound is structured can be overlooked, these qualities in some cases will start to manifest after a period of Valve Warm Up.
Valve when being assessed are needing a decent period of Warm Up, to let the settlement happen and for them to show their sweet spot, at least if it is a Valve that possesses a Sweet Spot.
I am not recommending a Valve, certainly not, the Valve of choice, in the condition wanted is as rare as Hens Teeth.
I am recommending time is allowed for each Valve used to manifest on to its better self.