Exposed roots shouldn't be a problem by itself unless somehow the soil there is being eroded away by something or seriously subsiding. What your issue is, if it is an issue, I don't know. Were they originally potted trees? That is often an issue because it causes girded roots.

What might be causing the roots to grow up?

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i would not expect that much root growth in less than a year .... are we sure they are from these trees???

only you can perfect watering at root depth ... take a hand trowel.. and dig some 3 to 6 inch holes in native soil ... and the gob you planted .. AND FIND OUT.... if its dry or wet down where the roots are ... absolutely no one else can figure it out for you ...

this type of winter damage after a transplants first zone 5 winter is not all that uncommon ...

is that weep hose even over the ball of media you planted???? .. were the plants potted or ball and burlap ... did you amend the [planting hole... give us more specifics on how they were planted ...

ken

about 100 arbs here, some are so bonsai looking. look at cemetary arbs as you drive by, both them and junipers are bare kneed. we love the surface roots they are so beautiful. if you can, plant a million pachysandra under them, or hostas, or blue bugle or prunella etc. pachys love helping out, and many do well under maples too. slow to spread though. we watch the little creatures steal our bird peanuts and try to plant thousands under our arbs. but with all this, i recomnmend also consulting landscapers or your extension group or conservation county for expert analysis.

I have maybe 30 arborvitae and they're tough as nails. I don't know what cultivar you planted, but they seem to be planted too close together. This probably isn't what's causing issues for you since they're newly planted. But, it might give you an excuse to dig some up and see what's going on with the roots. My guess is the soil may not be draining well and they're sitting in water. Might be too much root competition. May be nothing wrong. Just normal for coming out of winter.