Hear the words of wisdom of bodhidharma
Im still a beginner at this, specially where evergreen are concerned, so if I write any garbage information, may the wiser please correct me
I suppose that you already know about the different types of roots that occurs underground [ feeder roots, lateral roots, tap root ]
If not its better to have a
on those. They are kind of the basics before you can do any real root pruning that wont have any negative impact on your tree.
I've kill 2 trees because I root pruned some roots or sections that I should have left alone [ imo ] on a type of tree that was not "fit" for the root pruning regime I tried.
You should also understand how your tree behaves in relation with their root system...
For instance rosemary root pruning - never take off more than 1/3 of the root ball, otherwise you would very well kill the tree.
Deciduous tree usually have a more complex lifeline between the roots and the branches, meaning you could well remove any root that's annoying you in a deciduous tree if there is enough roots left to take care of the nutrients and water needs of the tree. You might need to reduce some leaves depending on the amount of root pruned.
In your case, this is an evergreen plant, those have a different type of lifeline relationship between the roots and the branches. You know those great looking juniper bonsai with lots of deadwood and a single line of greyish red bark twisting around the deadwood to reach some foilage at the top? Well this greyish red bark is your lifeline.
This means that the branches and foilage at one point, is dependent on some roots at the other end of that lifeline.
You let that branch die = the roots at the end of the lifeline will die too
You cut those roots prematurely = the foilage at the end of those roots will die in turn.
I might be oversimplifying things, but that's the gist of it.
Now back to your juniper:
What you did is a massive hair cut to the foilage. Meaning that some roots will be naturally eliminated over the course of time as the tree grows and establish/reinforce the lifelines. So for now leave the rootball as it is and place in a bigger pot to allow the roots to grow and the dead roots to rot away... it wont harm the tree.
When you will repot in 12 or 24 months from now, you will be able to identify the two type by their colors.
Dead roots = dark black.
Live roots = greyish red, to pale cream to white.
Discard / remove the dead roots and start working on the nebari.
Untangle the roots and spread them in a radial disposition around the trunk.
Then let them grow to thicken up - still in a training pot.
I've got two examples of what I did on a casuarina and a ficus retusa.
http://maubonsai.blogspot.com/2012/07/b ... ebari.html
http://maubonsai.blogspot.com/2012/07/f ... ebari.html
I've got a juniper but its still in training [ roots and branch movement mainly ] :
Flickr Juniper Bedfordiana in training
You should probably need as big or even bigger if you can find one. Dont look at the pot for the ficus, they could even grow in a crack in the wall, your juniper should be in a much bigger pot.
Im kind of wondering if you are using a "YouTube" video as teacher/mentor?
The steps you took sure looks like one of those quick and easy bonsai instructions on some youtube vids.
If you are using a youtube video, could you post the link so that we have an eye on how they instruct you to work on your tree?
There are some videos that are good, others that are ok and a third category that should be avoided until you know what to take and what to discard.
Well that's about it... Unless someone have a more detailed juniper nebari training progression, I would be interested in it too
Dont rush it... Like Dodhidharma said get yourself two or more trees. Use a correct method on one tree and train on the others. You WILL make blunders - I did and still do...
Train 1000 tree,
Create 10 potensai,
Master 1 bonsai
and done it somewhat correctly 
Ribbit, you sure have taken ALOT of foliage off, not to worry should be A ok but don't remove any more yet . You should leave it alone now to recover, read up on some Juniper topics so you get an idea of how they like to be looked after(water , fertilisers etc).
Ill make it my friend ive named it now and everything 
Thanks for the info about studying my tree ill see what i can learn 
