Hello Hairlove,
Recently, I tried roller setting my hair on big rollers (the big can size rollers from Sally's, and the grey next size down). My hair is texturized, and it's hard to get straight, and I'm about 7 months post relaxer. The rollers got my ends really straight---like I'd used a flat iron, and my new growth came out alright. Instead of rolling my hair under with the rollers, I rolled my hair going upwards, and the roots came out straighter. I also used various sized combs to comb each section before rolling it---I used a big detangling comb, and I also used a medium tooth size goody comb, to help straighten and smooth my hair out a little more. If you add a good amount of tension to the hair when rolling, it will come out straighter also---I'm still working on this.
The only downside was, I didn't leave the rollers in long enough, and if your hair is still damp at all, it will frizz back up, and mine did---I left the rollers in for 6 hours without heat. I think I could've used another 2-3 hours, or if you have a good working dryer, this process could be a lot quicker. It took me about an hour to roller set my hair. Oh! One more thing, the hair that I rolled around the can-size rollers, those sections got dry quicker, and the hair was straighter.