Can tube rolling change bass?

Bob, got the Peach II's specs from enjoythemusic.com

Specifications
Type: Vacuum tube stereo preamplifier
Line Stage:
Gain: 16.7dB in Hi Mode; 16dB in Lo Mode; 0 dB in HT BYPASS
Frequency Response: 5Hz - 90kHz
Hum and Noise: -85dB
THD:0. 15% 20Hz - 20kHz ref. 2V out
Input impedance: 47k ohms
Output impedance: SuperLoZ Mode: 90 ohms; HiZ Mode: 3.5k ohms
Max Output: 30Vrms 47k ohms load

Inputs/Outputs:
AUX Inputs (high level):4 relay switched
Tape Loop: 1 in, 1 out with monitor switch
Main Output: 1 RCA

Tri-Mode Operation:
The Mode Switch on the front panel has 3 positions:
LO: This is the SuperLoZ Mode with an output impedance of 90 ohms. In this mode the 6H30 gain stage is connected to a compound 6922 buffer stage to create the very low impedance output needed by some Solid State power amplifiers. In this mode the Peach will easily drive a 5k ohms load, or an extra long cable run.
HI: This is the HiZ Mode with an output impedance of 3.5k ohms. This is the shortest, most elegant signal path using only the 6H30 Class A gain stage and one capacitor to the output of the preamp. This mode is intended to be used with amplifiers that have an input impedance > 100k ohms, such as typical tubed amplifiers. We often refer to this as "BlueBerry Mode" as this is the same line out as the BlueBerry Xtreme.
HT: This is the HT bypass mode, or Unity Gain mode. In this mode the HT INPUT is switched directly to the output jacks as a "straight wire" bypassing all internal Peach circuitry including the volume controls. If you connect the FRONT outputs of your HT pre/pro to these inputs, you can put the Peach in HT BYPASS and control your front amplifiers from the HT Pre/Pro, making it very easy to use a premium amplifier for the front channels of your HT system as well as your music system. NOTE: The Peach must be ON to use the HT mode.

Outputs: Stereo via RCA plus
Tube Compliment: one 12X4, two JAN Philips ECG 6922 and, one 6H30
Dimensions: 19 x 6 x 12 (WxHxD in inches)
Weight: 18 lbs.

Obviously, I should have also noted, perhaps more importantly, that one may or may not like the sound "coloration" per se provided by the Mullard/Brimar combo. I place quotes around the word coloration because some consider it a departure from the reality of so-called unamplified music. In most instances I would reject such a claim, since widely varying colorations are found from concert halls to open air venues(with effects produced by wind, humidity and air temperature)as well as being associated with equipment that involves the recording and reproduction of sound in the studio, audio salon and home. Further, this may raise questions regarding the validity and/or meaning of the word neutrality.

To answer your question, tube rolling can affect bass to a minor degree. FME, bass is mostly affected by the room and speaker location. Smaller bass adjustments can be had by equipment, amps, preamps etc. Smaller yet bass adjustments can be had by cables and power cords. Tube rolling comes in next, and probably last for bass adjustments. You can find some tubes that may have some minor affect on bass. In my tube rolling experiences, I've noticed most differences in tubes lie in the midrange, high's, soundstaging, and aspects like that. Bass to a much lesser degree.

Cheers,
John

Usually the tube rolling can change the sound signature slightly. So the difference is not bigger.