When you say that the area that has root-curl fizzles out at the ends, do you think this might be due to damage of some kind (i.e. have you had a relaxer, or over-done it with heat styling, etc.)? And are you CG?
And do you know what your hair properties are (porosity, texture, etc.)?
I'm not trying to bombard you with questions, but the answers to these might help to find a solution ad to why this is happening.
Medium/coarse, low porosity, mix of 3s Low-poo: SM Moisture Retention
CG (again) since Nov. 2012
Co-wash: SM Conditioning Cleanser, VO5 Shea or Kiwi-Lime
Condish: AOHR, GVP Balm, Cure Care, Giovanni Direct
Protein: AOGPB, CNPF
Stylers: KCCC, SM Souffle, AOMM, SS CEJ, Deva ArcAngel
Trying out steaming!