Both tube rolling and cap and resistor upgrades will improve sound quality. Only question is cost effectiveness. I'd say go for it, while you may spend as much or more than amp originally cost, its a learning experience. Better to start learning on cheaper equipment.
I started learning about parts substitution on cheaper equipment, such that I now trust myself with more expensive equipment.
I recently changed out caps, resistors and all tubes on PrimaLuna Dialogue Four. Miflex, Mundorf caps, Takman resistors, NOS miniature tubes, SED and Svetlana EL34. Sound quality improved to the extent I now consider this amp a real contender to totally stock Coincident Turbo 845. Prior to mods, sound quality just ok.