I would treat this just like as if it were the regular soil that makes the contents of a reg. garden. Just stir up the soil mix in all the supplements and plant.

I concur, the fine roots won't be a problem at all. Removing the larger roots is a good idea simply because their presence can make it difficult to get the next plant in, but beyond that the roots won't hurt anything.

It's also fine to remove the mix and break it up and remove some of the fine roots in the process if you wish, but much of the time those fine roots will be at least partially decomposed by the time the next planting season rolls around (assuming we are talking about next year)

Well, no actually - not for next growing season. I'm referring to using it right now! As mentioned, I want to plant a couple of cool-weather tomatoes here in San Diego so I'm ready to plant right now ... so, is that STILL okay then to reuse it right now?

I wouldn't reuse the soil. Here's why, recently posted on another thread, by member Tapla (Al):

"In my estimation, the only case to be made for reusing container soils is one of economics, and you'll never find me argue against making that decision. If you can't afford, you can't afford it. That said and setting economics aside, you might decide to reuse soil for reasons other than economical. Perhaps the effort involved with acquiring (or making your own) soil is something you might not wish to go through or be bothered with.
In any case, it would be difficult to show that soils in a more advanced state of structural collapse can somehow be preferred to a soil that can be counted on to maintain its structure for the entire growth cycle. So, if the economic aspect is set aside, at some point you must decide that "my used soil is good enough" and that you're willing to accept whatever the results of that decision are.

All soils are not created equal. The soils I grow in are usually pine bark based & collapse structurally at a much slower rate that peat based soils, yet I usually choose to turn them into the garden or give them over to a compost pile where they serve a better purpose than as a container soil after a year of service. Some plantings (like woody materials and some perennials) do pretty well the second year in the same bark-based soil, and with careful watering, I'm usually able to get them through a third year w/o root issues.

Watering habits are an extremely important part of container gardening. Well structured soils that drain well are much more forgiving and certainly favor success on the part of the more inexperienced gardeners. As soils age, water retention increases and growing becomes increasingly difficult. If your (anyone's) excellence in watering skills allows you to grow in an aging medium, or if your decision that "good enough" is good enough for you, then it's (your decision) is good enough for me, too.

The phrases "it works for me" or "I've done it this way for years w/o problems" is often offered up as good reason to continue the status quo, but there's not much substance there.

I'm being called away now, but I'll leave with something I offered in reply on a recent thread:
"... First, plants really aren't particular about what soil is made of. As long as you're willing to stand over your plant & water every 10 minutes, you can grow most plants perfectly well in a bucket of marbles. Mix a little of the proper fertilizers in the water & you're good to go. The plant has all it needs - water, nutrients, air in the root zone, and something to hold it in place. So, if we can grow in marbles, how can a soil fail?

Our growing skills fail us more often than our soils fail. We often lack the experience or knowledge to recognize the shortcomings of our soils and to adjust for them. The lower our experience/knowledge levels are, the more nearly perfect should be the soils we grow in, but this is a catch 22 situation because hidden in the inexperience is the inability to even recognize differences between good and bad soil(s).

Container soils fail when their structure fails. When we select soils with components that break down quickly or that are so small they find their way into and clog macro-pores, we begin our growing attempts under a handicap. I see anecdotes about reusing soils, even recommendations to do it all over these forums. I don't argue with the practice, but I (very) rarely do it, even when growing flowery annuals, meant only for a single season.

Soils don't break down at an even rate. If you assign a soil a life of two years and imagine that the soil goes from perfect to unusable in that time, it's likely it would be fine for the first year, lose about 25% of its suitability in the first half of the second year, and lose the other 75% in the last half of the second year. This is an approximation & is only meant to illustrate the exponential rate at which soils collapse. Soils that are suitable for only a growing season show a similar rate of decline, but at an accelerated rate. When a used soil is mixed with fresh soil after a growing season, the old soil particles are in or about to begin a period of accelerated decay. I choose to turn them into the garden or they find their way to a compost pile.

Unless the reasons are economical, I find it difficult to imagine why anyone would add garden soils to container soils. It destroys aeration and usually causes soils to retain too much water for too long. Sand (unless approaching the size of BB's), has the same effect. I don't use compost in soils because of the negative effect on aeration/drainage. The small amount of micro-nutrients provided by compost can be more efficiently added, organically or inorganically, via other vehicles.

To boil this all down, a container soil fails when the inverse relationship between aeration/drainage goes awry. When aeration is reduced, soggy soil is the result, and trouble is in the making.

I've mentioned before that I don't post here to get people to convert to a particular mix or blend of soil. I post what I know will work very well for anyone who can get appropriate ingredients & modify the mix to suit their climate & other cultural conditions. If you use a mix that guarantees good aeration for the expected life of the planting - you're in good shape. Most peat based mixes will not work well in extended life plantings. Conifer bark based mixes, on the other hand, retain structure for much longer periods.".

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There's one other reason. Tomatoes and other vegetables are susceptible to all sorts of soilborne pathogens, viruses and fungi. This is why vegetable growers and farmers rotate crops on a regular basis. Using new soil in a container is the same thing as rotating crops in a veggie bed.

... so, is that STILL okay then to reuse it right now?

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I agree with all the anwsers above even though they seem to be different. The variable here is determined by what "OK" means. There are some people who are unhappy with anything but the highest performance and production from each plant. I am one of those. And this forum has been a God-send in educating me as how to do so. It is like living nextdoor to expert gardeners on every side.

But many of our fellow forum members have been growing tomatoes in garden dirt in plastic bags for years and are happy with the results. And many EarthBox users are quited please that they have reused the same media for many years. For me, that might not yield the results I am looking for, but for them it is "OK".

This year, before I learned thru this forum the right way to plant tomatoes in containers, I planted 32 plants in whatever I could find: plastic bags in office crates, used pots of various sizes, whatever would hold dirt. I bought one earthbox, just to try it, but the rest are in "make shift" pots. I have nothing but sand in my yard so I dug some dirt from the forest and a little lake muck from the lake and, yes, added a little sand to the mix along with a whole cup off vermiculite to each 5 gallon+ container. (Do you think helped?)

When I learned thru this forum that I had just put one of the worst container mixes possible in all my pots I added a little peat and perlite to them and decided it was going to have to be "OK". I've been picking on the average of 60 tomatoes per week for almost 6 weeks and enjoying the best gardening experience I've ever had, even though it is not what it should be. I have had no diseases on any plants, except a little some BER here and there.

So, for this year this has been "OK" for me. And if I was more casual about my gardening I might do the same thing next year, but for me it would not be "OK" for next year.

I am planning on using Al's mix next year on all my tomatoes, but I will prabably re-use this mix for a few years, until I run into fall-off on production or some other problem surfaces. Because if I had to replace my soil ever year it wouldn't be "OK" with me, because part of my fun in gardening is the economy and simplicity of it. That's why I am using Al's mix and planning to convert all my pots to self-waterers next year.

So you've got to process all this information and decide what's "OK" for you, what's most imnportant for you: economy, simplicity, higher production, healthier plants, etc.

Since you in one of the nicest weather areas in the world I'll guess your tomatoes won't be overly stressed by heat or cold, so disease may be less of a threat. If I were in your location I'd re-use the soil. But others would change it out. Either way can be "OK", depending on your goals and priorities.

Have fun growing. If you need any help eating those tomatoes in your 70 degree weather come January, let me know. I'd be glad to come down and help.

Bob - from Wisconsin, who will be snowmobiling : ) in January but not picking tomatoes : (

PS. What kind of tomatoes are you planning to grow?