I use velcro rollers every day. My hairs sounds alot like yours as well...fine, shoulder length and straight and I am also from the humid South! 
I stopped using flat irons/curling irons last June because my hair was just horrible (dry and split ends etc). I also tried WEN (and love it).
I still wash my hair everyday and blowdry on the coolest setting. (I just dont feel right if I dont wash my hair)
I use Big Sexy Hair "Root Pump Plus" (spray alil on my roots before I blowdry)
After my hair is dry I tease each section alil before I put it up in the velcro roller and spray a lil Big Sexy Hair "Spray and Play Harder" hairspray. (I have a "waalaa" teasing comb for teasing)
I like using the larger velcro rollers and pop em up after I blowdry, I blast them with alil heat from blowdryer and let set while I do my other morning stuff....like coffee! 
I get volume with alil curve from the big rollers.
Maybe 2-3 times a month I use the Calista hot rollers (long) if I want curls that day. takes about 5 minutes....by the time I put them up I start taking them down. I get curls and volume with Calista.