i vote roo. he has a roo-ish stance and his comb is pretty big. my hens didnt get a comb like that untill they had been laying for a few weeks. not to mention his tail (or lack there of) looks roo-ish
I had RIR and thought I knew all about them and could tell the roos apart really well. They got beefier and developed their red bits so much faster----but I found out I was so wrong when I gave what I thought was one roo and two hens to a friend (18-20 ) weeks old only to find out later they were two roos. It seems RIR can be sneaky (especially not a dominant one) and not develop till so much later. At 18-20 weeks these birds weren't crowing either not even the extra large oh so masculine one.
Now if that bird you have is a girl it is so red you must be expecting eggs
I have a suspicion this is extra difficult because it appears you have a mock-rumpless, if I'm not mistaken. Feel the back end of the bird- is there a separate digit-appendage- for the tail? I think what we're seeing is tail feathers growing out of the rear without the actual tail stump. There should be a triangular fleshy, muscled tail there that can be swished. If not, then it can still have tail feathers, but they just grow out and sit there. That's what I think I'm seeing, anyway.
If the tail feathers taper to a point, they're likely roo feathers. If they end more of a fat, blunt end, then you likely have a pullet.