I would say a rooster, judging by the size of his legs and his height difference in relation to the others around him, unless he's older, but his legs are quite a bit bigger in comparison to the others
ETA-sorry you said they were all 13 weeks So yeah I would say he's a he
I'd say pullet, not roo. But it's hard to tell with BOs - there was one in my flock that everyone else next to her flock mates looked huge, larger comb - otherwise intelligent people assumed she must be a roo. Then she started laying eggs - double yolkers for a while, just to make a point, LOL.
That's too funny, I swear they fool me, every time. I think they are roosters until they lay they get loud ,and they are so big. I love the breed though very friendly mine come running when they see us then they jump us if we don't pick them up fast enough. I wonder what the roosters are like but I love my neighbors so keeping the peace.