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, dense, mix of 3s
CG (again) since Nov. 2012

Cleanse: SM Moisture Retention, Elucence MBC, KC Come Clean
Condish: Giovanni DL, Cure Care, Ion Treatment, GVP Balm, AOHR
Stylers: KCCC, SM Souffle, AOMM, SS CEJ, JCRR, JCCC

Trying out steaming!