I usually trim the roots back to 2"-3" for planting ease, and have had no noticeable problems.

Hopefully others will reply.

I don't trim the roots. Those look freshly dug, so if you can dig big enough holes, I'd plant them the way they are.
Renee

you might shorten the roots up a little bit, but the longer the root the better you can get them to stand upright in the ground. I've gotten iris from e~bay sellers where the roots were non existant because they were totally trimmed off. they were extremely hard to plant because there wasn't anything left to make them stay upright. so, all you can do with iris like that is just put them partly under the dirt & hope they make some new roots on them. so, if you do shorten the roots that's fine just don't take them all the way down to the rhyzome, because then you'll have trouble planting them.
that's a nice grab bag you managed to find. good job.