Not trying to steer ya away from A/F,but,as you can see,not too much activity here w/this particular phone.
I'd keep an eye on the FLEX forum over @ XDA for info on root related topics.
FWIW,there's not much activity w/the FLEX over there either,but,if anything develops with KIT-KAT/SPRINT/Root,it'll be from the membership/developers over there 1st,then,info will make it's way here.
As for the more popular phones,lots of activity here,but,as I found out myself,if you have a niche device (such as the FLEX,or for another example,the QUALCOMM TOQ smartwatch,which I own),your best bet is to start w/XDA.
I subscribe to the FLEX forum,if I find anything new,I'll post it here.