Originally Posted by
Biomega
RoF should generally be maintained constantly, provided it will deal damage throughout its full duration on one target, or a proportional amount of its duration on multiples.
As for when to cast it, as long as you waste no procs, you can slip it in whenever. Warlocks in general are all about proc-management; you don't want Backdraft to go unused, you want to maximize your damage during trinket/enchant/racial/raid procs. RoF, while dealing some damage, is mainly used for ember-generation. Do not try and maintain a 100% uptime if that means not getting in that extra buffed CB. Consequently, do not use it if it means capping on embers, either, or capping on Conflagrate charges.
That being said, our "rotation" is fairly simple and fast-paced, so it should be easy to squeeze in RoFs with little downtime.