Is there a reference sheet I can print for the characters?
Good rule of thumb: when looking for a reference for a board or card game, always check BoardGameGeek. Here's the most popular Citadels reference available there:

https://boardgamegeek.com/filepage/18772/universal-head-citadels-reference

And you can find a ton more in the Files section of the Citadels detail page.

(I believe you have to sign up for an account to download files off BGG, but if you're into board games it's totally worth it.)