I think the better question would be: Why do you want to incite the crowd? If you just want to do it, because you could, then there is not going to be any need to roll.
Mostly though, I think you can treat a crowd as a single entity, because none of them is important as an individual. Maybe give them one guy as a face (who might eventually become a real character).
After that, the important part becomes, what you want to do with them.
Let's say you are being chased through the city and are dangerously close to being caught. You can use the crowd as a block, using the result of your incite roll as the block value. If the crowd is particularly large, so it would make for a better block, you can declare that first and then tag it on your roll.
Same, if you want them to serve as a human shield against a wizard, for example. If however the attacker does not care if he hits innocents or not, the block would not work against him.
It should work for anything else, as well. You could attack with a crowd, using your incite to inflict physical stress with the crowd as a proxy.
To make it harder or easier to control them, you can declare an aspect reflecting their overall mood. A crowd that is already angry is not hard to push over the edge.
