The root pruning timing issue was raised in another thread with subject "Revised Thinking about growing in pot". It was felt that a separate thread needs to be started for this purpose. So here it is.

Also, it will help to know the symptoms of issues when the root pruning is not done when it was required other than having difficulty in poking a stick in the soil.

My observation with plants that required pruning but were not pruned showed fig fruits staying small, wrinkled and fluffy and tendency to fall. Also the water penetration becomes slow.

My Opinion is to prune in The Spring,just when you see the buds begining to grow fat,and green.
This is the time the fig is rested and willing to grow new parts if needed.
The tree start dying from the tips of the roots,and from the tip of the Branches,so if the tree suffered from lack of anything,in the winter then you will find dead roots of the extremities.
You cut those off first and see what you are left with,and make an informed decision,about the state of health of your plant.
This is what i do.

My experience has been just after dormancy.  If I were still growing in containers, this would be what I would be doing.  The roots will continue to grow even if the top is dormant providing the temps are above ~55F.  The advantage to doing root work just after dormancy is the roots have time to rebound during dormancy and top growth will be more vigorous when the tree wakes up in the spring.

When i root prune.
I root prune before bud break when weather here is moderating and i pick a nice day for it so i dont freeze doing it in garage. Yet plant is still asleep.
After im done root pruning i go right to the canopy and prune it along with more shaping of tree to my desire and any unwanted crossing branches in middle for added sunlight.
Little hint right before budbreak try rooting some scion when you trim as i feel this is time when you get the best strikes with them.  ; )
I make a mess in garage yes !

My experience in past and this season when plant is rootbound and what i have to do.

More slower frequent watering is needed to penetrate deep into root system. I say slow because if you dump water out of bucket it will just run down the sides of pot and not where its needed.
I resort to useing a tree root feeder with hose attached to it - much easier in these times of tree being rootbound to water it and i put the water where i want it - the entire rootball.
Some fruit on plant will fall before maturity and some ripe fruit may have a little less moisture inside .
Over all i have experienced a reduced crop with a rootbound tree , so rootbound you cannot "scrape" your 4 forefingers into the soil without grabbing a bunch of roots at soil level.
  

I have no experience, but two of my plants will be root pruned this fall upon entering dormancy. They are in pots; pots sunk into the ground, and judging by the top growth there has been lots of root growth as well. I'll put them in bigger pots at the same time.

Grant
Z5b