I would say add 6 more males, so it will take you to 8 males.
It also does not matter if you have 30 males with 24 females, they will still do what they programmed to do!.
You also have to look at the bigger picture of breeding, a females gestation time is 28 days so call it a month, if all the females are mated they will take one month to give you some nymphs.
You have to take this into mind, males shelf life is not that long, especially with all the mating going on between the 2 males and 24 females. But on the other hand, a male needs to stay alive for 28days or longer to be able to keep the roaches flowing.
The reason I say this is, if all females are mated and gravid at the same time(Don't think that should happen) then the male will have nothing to do with them selves for 28 days, and like I said the males seem to die off