Unsolicited chick picks. Do I have a couple of roos in my flock?

I have 10 chicks, approximately 3.5-4 weeks old, an older bunch, and a younger bunch. The ones in question are the Leghorn from the younger group, and the Jersey Giant (I think it's a Jersey Giant, anyway) from the older group. At first, I suspected Nugget, my Amberlink, and Dottie, my California tan, from the older group, may have been boys, but now that they've gotten a little older, I'm thinking they're probably just big, bossy hens. I also have 2 Black Sex Links and a Leghorn from the older group, 2 Rhode Island Reds and another Leghorn from the younger group. The older Leghorn is about the same size as the 2 younger ones.