Here are the possibilities:
1. You could have a hen with lots of testosterone (happens occasionally when there are no roosters around - these hens make the motions of mating the other hens, and even get enlarged reddened combs.)
2. Your roo could be hanging out in nest boxes, as do many roos. Especially when the hens are laying.
3. Yes, your roo COULD be a hermaphrodite!
Because you already know the egg appearance of your other hens, the latter certainly is a possibility.
Remember, the other hens aren't laying because of Mr(/s). Roo. They would lay eggs without him - it's just their biological workings. If he/she is in fact a hermaphrodite, then it is possible the other hens' eggs are not fertile, though. Usually in hermaphroditic animals one of the reproductive systems, although present, is not actually functional. If the ovaries are functional, then the testes probably aren't.
Hope this was helpful! (And now, all seriousness aside, I'm giggling, my butt off...)