It would have been better to get the plant out of the pot carefully, preserving what you could of the dangly roots (possibly even cutting away the pot if it was plastic) and then potting into a large one for now until spring comes and you could more safely cut roots. At that time you could have looked at the rest of the rootball to see if in fact there were many roots circling the ball, and (again) put it directly into the larger pot til spring. That's the part that counted - how rootbound the rootball was/is, rather than cutting stragglers. However, as you've done that, you might as well slip the whole thing out of the pot carefully, see if it could use a larger pot, and slip it into one, just backfilling around the sides and nothing else. It's not time to be pruning roots wholesale.

Thanks for the advice. I should have posted before doing anything.
SIGH
How786

I heard back from the man who sold me the bonsai. Here is what he said. I will definitely follow his advice.

"I'm glad to hear that the trees look great! It's great to hear from you!
The roots coming out the drainage holes mean two things:

You have an extremely healthy and vigorous plant
There was probably a lot of humidity trapped underneath the pot favoring the root growth. Make sure water flows freely underneath the pot after watering.

You can definitely cut them back. Doing so keeps the drainage holes unclogged. It does not mean any harm to a healthy strong tree.
Never repot this time of the year.
The time for repotting is early spring, before all the new growth start. The serissa may need to be repotted then, but that has to be determined yet. It should be ok for one more year, but it will depend on how well have you cared for it in terms of watering and feeding, and how much new growth have occurred, in which case repotting might be necessary next year. To determine so you just have to lift the tree from the pot like you did to change the pots for the forest (let it dry for a day or 36 hours before) and see the bottom of the root mass. If you see all roots and very little or hardly any soil you definitely need to repot.
You can repot using the same pot, or you can use to go for a slightly larger one. If you prefer to do the second just let me know and I will be happy to find a suitable one.
You can keep the serissa in the same pot because when repotting you prune (cut off) approx. 1/3 of the root mass, and replace it and any loose soil lost with fresh new soil. Usually this time is used to prune the branches and leafs, which balances off the tree. In such case there is no need for a larger pot, and is usually a matter of aesthetics. You should be careful that the pot do not visually outweighs the tree, though. In the case of your serissa you can definitely go for a larger pot and it will still look stunning!
In any case do not worry about anything of this right now. Just wait for early spring and we will get to it. If you want the new pot now just let me know, and give me the measurements of the current pot (length, width, depth). Otherwise we can work on that too in the spring, is totally up to you, there is no rush and hence no need for me to sell you something right away when you can use that money for something else (halloween treats ...lol)."

How,
The advice that your seller gave to you is both wise and non-alarmist. I'd do exactly as he says to the letter.
He/she sounds like a great person to work with, a very experienced person!
Ginny

I was suggesting a 'slip-potting' which is not 'repotting' in the sense he means it - that does entail root work and should not be done now. What I suggested was a way to sustain your tree until spring (if it looked rootbound) by 'slipping' it as a whole from the pot (even to the extent of cutting away the old one) and directly into a new one, with added soil on the outside. It's done all the time with zero consequences for the tree, and done when necessary to deal with very rootbound situations - sometimes you have to use common sense rather than rules - if a tree is in danger due to a specific problem, more so than it would be if you just wait til the next season, you need to act (carefully).