Despite your handle you don't seem to be all that inquisitive, in fact you seem to be down right confused
The roller on the J model is part of the basic fit, is accounted for in the -9
is included in the basic weight and index calculation and remains on the aircraft at all times.
When not on the floor it is stacked up to 3 high on top of the permanently fitted -4a side guidance system and as AIDU states it takes about 5-10 minutes for a couples of guys to lay or take up.
So your statement "I've flown plenty of 'frames that have not had roller on board anywhere" is actually pants and I would humbly suggest a couple of sessions with the latest copy of Jane's to help you sort out your recognition issues