You do not need to root to put a new ROM on.
Go to the dummies guide to see how to put CWM on and a new ROM. Here: http://forum.xda-developers.com/show....php?t=2317500
And yes, you need an SD card to do all that.
If you just want to root stock and not install a new ROM, go to my HD/HD+ CWM thread linked in my signature.
Sent from my BN NookHD+ using XDA Premium HD app
See my Nook Color Tips Thread here
and my Nook Color EMMC Partition Repair Thread here
and my Nook Color Updated CM SD Installation Instructions here
and my Nook HD/HD+ stock tips thread here
and my Nook HD/HD+ CWM Root Tools thread here
e.mote's Nook HD/HD+ Dummies Guide for installing CM10.1/CM10.2 here