See the droopy, curved feathers just before the tail? Those are rooster indications. Also look at the feathers in the cape/neck area. Roos have pointy tips on those feathers, hens feathers are more rounded at the tip. If you see feathers that come to a split point, either in the neck and cape, or in the saddle, having two distinct sharp-angled points, you have a roo.
Sometimes in very young birds, when they first feather out, pullet feathers will look somewhat pointy, but by the time they're growing out curved sickle feathers, like your two in front there, they've become more definitive. I can't see the back end of that third one well enough to tell, but the white one in front is a boy, and I'm pretty sure the black one is, too. The third one in back, looks like the feathers in the cape have rounded tips, that one could be a girl. It's hard to tell the shapes of the tips feathers by a photo, though.