[LG G Pad 7 ROMs, Kernels, Recoveries, & Other Deve] mmhere:
I'll report my experiences in getting the new ROM (20151013 from SultanXDA --Great! --THANKS!) going with root recovered, where I was unable to use root on the first go -- in case anyone else finds the info collected here to be useful.

I flashed the new ROM over the top of the current installation (20150706 in my case) and made sure to flush cache and flush DalvikCache before rebooting.

At this point I did not have root when booting into the new ROM. SuperSU was still installed from before, but when run, complained that it could not find the su command. As I mentioned earlier I went back to the previous ROM with all of my stuff installed via the Nandroid backup i'd made before trying the new ROM. This way I entirely started the process over. Do a Nandroid BACKUP!

Next time around, I loaded the same new 20151013 ROM and was prepared by first having the SuperSU.zip file ready on the same uSD card in the same location as the .zip for the new ROM. So I loaded SuperSU from .zip while inside TWRP at the same time I loaded the new ROM. I flushed caches and went again.

P.S.: the relevant SuperSU threads for downloading that package, either the stable one or the beta one [which i used] are here:

http://xdaforums.com/showthread.php?t=1538053

and here

http://xdaforums.com/apps/supersu/2014-09-02-supersu-v2-05-t2868133

Still did not have root.

So I went into settings to look under Developer Settings (already enabled by me previously) but for the life of me I could not [and can not] find the "enable root" or "allow root" setting under there; pretty sure it should be under there but it isn't. Is this ROM missing this specific option? Or is this a Lollipop thing?

Ran the SuperSU app while booted into the new ROM. Even tho SuperSU did not complain at this point [like it did before] about there being no su command, I couldn't get root any where (tried su in terminal, or /system/xbin/su to spell out the path directly), then id to check for achieving userid 0, but this did not happen.

So it turns out SuperSU has a setting to indicate whether or not it should "obey" the developer settings (cyanogenmod settings?) as to whether "allow root" is set over there. If you make SuperSU IGNORE this setting (uncheck the SuperSU option), then root happens under the auspices of SuperSU.

Now all of my apps that need root permissions (terminal for when I'm messing about, SaMBa, adblock, etc.) are now happy to run with the permissions they require.

TTFN

---------- Post added at 16:57 ---------- Previous post was at 16:16 ----------

So I should have RTFM'd!

I see this note under SultanXDA's Changelog for the 2015103 ROM:

Changelog:
October 13, 2015:
ROM:
...
*Removed built-in superuser (use SuperSU instead)

So the regular Developer Settings option to allow builtin root/superuser is indeed removed. You must disable the SuperSU setting Respect CM root settings, because the default setting cannot be accessed. With no access to that, SuperSU will always respect the default state which is: NO ROOT.

That's a little bit confusing, and should perhaps be called out more explicitly for those of us who need ("want?") root capability.