That is 100% rooster...If you want keep him and you will see. Just curious if he is a ligth sussex then you paid alot of money for him why would you give him away?
...but I think HE'S a hatchery stock Delaware. I've seen young Dellie roos with solid tails like that...sometimes they moult them out to barred, sometimes they don't. The light yellow legs are typical for hatchery Dels, too. Most all of the hatchery Dels closely resemble Columbian Rocks, especially in body type. And those wattles are just too pronounced for it to be a hen of 11 weeks old.
I would seriously doubt that TSC would ever, even accidentally, have light Sussex.
I think most definatly a rooster. I have one too from TSC- see my post for free rooster in CT .... my Foghorn looked identical to yours at that age - and he's earned his name well.