nothing. palm rolling, crocheting, root rubing and everything else is a waste of time. only thing you should do is keep them healthy and clean
if your locks start trying to join other locks and you want smaller locks just pull them apart. thats all you need to do. although crocheting makes your locks look more mature, all it does is pull the loose stuff in the lock. the hair is still pretty much loose, but out of sight and constricted. i heard it can damage your hair too but i haven't seen it for myself (makes sense, poking holes in the structure can't be good.) palm rolling is a complete waste of time, if you want to keep crocheting go ahead, but cease the palm rolling. it does basically the same thing as crocheting, pulling the loose hairs close to the lock, but instead it is less effective and a lot more stressful on your hair.
I totally disagree. I think palm rolling is pretty much benign while using a crochet hook rips hairs apart and pulls loose hair out. Palm rolling doesn't do much at all but unless you are rolling it hours, you really shouldn't see any damage. If anything it just straightens the dreads and keeps them separated to a degree. But with the crochet hook you are puncturing the dread and every time you do so you are breaking strands of hair creating more loose hair that you have to later crochet back in only to create more. Plus, you can tell a big different between naturally dreaded growth and the part that has been crocheted. So if you don't wish to continually crochet your hair just to keep it looking consistent, then I would advise against it all together.
shadygrov is right, listen to their advice. honestly though, all you have to do is separate the locks, and if you do decide to do some "maintenance" be as gentle as you can. for palm rolling you've probably seen those instructional videos where someone grabs a lock, pulls it straight and goes nuts back and forth. well if it looks rough, thats probably because it is, so be gentle when you do it, don't tug on your hair or stress it too much. personally, i rub the roots in the morning when im drying my hair. it makes them frizzy and easier to work with so i can guide them back into the right lock. if you haven't already, you might want to try that out and see what it does for you.
all i do is rip them apart. but lately i havent encouraging congos. almost every dreadlock are conbined/ing with another (cause when i started i had thin ones) now i have 2-4 dreadlocks combining. few years it'll look real good