exchange 2013 and edge role

Hi,

I have all exchange role installed all is working fine without edge role. CAS is load balance with nbl and MBX is with DAG. If i involve edge do i have to deploy multiple role and do same NBL for load balance, if i invovle what would be my dns setting will this point to edge role, what owa url will point to edge or remains on cas if on edge do Edge have to redirect to cas or ressovle itself the request. 

Your Guideline regarding edge

thanks