Presumably it is recommend to carbonate before conditioning, rather than after? Especially if you roll the keg around!
Or why not just keep it at serving pressure (usually about 8PSI) with the gas bottle and regulator connected during the entire conditioning period?
It does make sense to roll it around though, since it will greatly speed up absorption of CO2, just like shaking an already carbonated drink speeds up the release of gas.
I read where a recommendation to give it 2 days at 40PSI, then reduce to serving pressure. I'm unsure if one is supposed to simply wait while that CO2 is absorbed and the head pressure reduces, or leak off the gas?