Blood of Dragons is designed to be a game that is not too dependent on specific roles to be in play for roleplay to flow smoothly. Since all characters of importance already exist in the CDB, if a specific character who is needed for a plot is unplayed, the Admin can allow the character to be played temporarily or they can simply decide how the character reacts.
That said, as the focus on the game is on court life and court politics, the Admin are particularly interested in concepts for politically involved characters. Players who want to play characters that hold offices at court are not restricted to finding characters already placed in such positions, they can simply request any character who could feasibly hold an office and propose what office they would like to hold during the application stage. The Admin are always happy to work with players to find a suitable position at court for their characters.
Beyond this, the Admin would like to encourage players who find themselves asking what is needed to consider what sort of character they would most enjoy playing. It is our experience that the more a player enjoys a character, the more useful for the game that character is. If you still find yourself at a loss and would like some sort of suggestion, there are two things you can do.
First, take a look at +cdb/wanted. This is a list of the top 10 most wanted NPCs on the game, as voted on by the players. Secondly, if none of the entries on the list appeal to you, you can also have a look at the forums. There are stickied threads there dedicated to players advertising for specific roles that they would like to see filled and it is also where the Admin sometimes advertise for specific roles or concepts when we do feel a need to do such.