My boom stays attached to the sail... I do not see any benefit from taking it off. Removing the sail from the boom would make more sense with a sail that is not fully battened or if you would take the battens out. On my mono hull I could fold the sails very compact.
I prefer folding over rolling. My folding technique requires two people. With the sail lying down, starting at the boom, one person positioned at the luff one at the leach, both people simultaneously reach for about 40 cm of sail, fold it over, repeat...
Patrick