I don't really recommend Rom manager to partition cause if it goes wrong you still need something like gparted to fix it.
Although unrevoked replaces the native recovery with clockwork on the true sense (flash), Rom manager uses fake flash. By that I mean it doesn't use the proper version you have, rather it downloads a second version, puts it on sd card an applies it as an update.zip so if Rom manager is really the way you want to go, you still have to download it via rom manager a second time to partition