How do you know that you downloaded a new fimware or just some application updates?
Did you take note of the software version? (Under Settings/About/Software).
Did it give you any warning about losing your Apps? (Titanium Back-Up is for backing-up Apps).
You can not "roll-back" firmware if you did not do a ROM (also called nandroid) back-up first...
But don't dispair, because If a ROM is not working for you, wether it is stock (Manufacturer) or not, you can get something better here!
Check this post out:
Cheers, and don't despair, rooting is just the first step to a long and fun path!
BTW, you might have to root it again, but you already know how to.
---------- Post added at 08:12 AM ---------- Previous post was at 08:08 AM ----------
Opps.... Forgot to ask... Did you do a "reset" (Hold Power down and choose reset phone)? A simple reset can solve A LOT of things, better
than just pulling the battery out, so try that first and let us know what happened.
Again, you have to ENJOY getting into phones. You will learn a lot while failing and trying again!