If you're positive they are completely dead, yes.

will it make new roots? Does it matter if I just squish the roots into the hole? The instructions say the hole should be 4". Does that mean 4" plus space for the roots to be straight down?

Yes to the extra space for the dried out roots. It's what I would do in hopes of success (bury the roots). Siberians aren't like some plants where you have to be careful not to cover the crown.

I would also find a location where it doesn't receive sun all day long. Houston's summers are probably very hot and few overcast days. The link says more.

Since the roots look totally dead there is no guarantee the plant will live. All you can do is plant it, thoroughly water it in, and continue to keep it moist. Give it a couple of months to see if it will revive. Good luck.

Here is a link that might be useful: http://www.socsib.org/ssicult.htm

when you cut something off a plant.. you are opening a wound ...

as compared to natures way.. of closing off an area.. and letting it rot away ...

just dig the hole you need.. to plant it .. properly.. according to the type it is ...and dont cut anything off ...

ken