Might this be a roo?

[Heather01]

It is larger than my other chicks and the comb is more prominent. Wattles seem red, too. Four weeks old

 

[Chicken Girl1]

Picture isn't showing up :/

 

[Heather01]

Sorry about that- fixed it

 

[Choco Maran]

Looking at your picture I would say NO it is not a Rooster. What breed is it? It might be that it is just a larger breed then the rest of the chicks you have