The Romans can use Glory of Rome to get their conquered cities online faster (cheap Courthouses)...
Kinda off-topic but I would not be surprised if you cannot build a courthouse in your capital city. The point of the courthouse is to remove the penalty for annexing a city and since you cannot annex your own capital it would have no benefit ASIDE from Rome's bonus and from the looks of things Firaxis is not of the mind to allow a rushed courthouse.