When setting up a game, you have two steps: Choosing roles and assigning stuff. Here are some tips:
For selecting roles, you need one of each category. Use http://www.random.org/sequences/ to get random numbers, but basically do the below:
Saving: If there are 10 saving roles, get a random number from 1-11. If you get 11, instead get a random Universal role to replace the Saving role
Investigative: If there are 10 investigative roles, get a random number from 1-11. If you get 11, instead get a random Universal role to replace the Investigative role. If there is already a Universal role, ignore choosing a second.
Repeat this for each category and then post links to the seven roles. If you got a Universal role, you may have to repeat the process to follow changes to game setup.
Then it's time to assign stuff to players. Using the same randomizer, go ahead and get the numbers of the random players who are to be mafia, then random players to have roles. make sure all the mafia don't have roles! If needed, randomize a few more times to assign secondary roles. Remember: secondary roles can be given to roled and mafia players, even multiple times. We once had a player with three secondary roles.
If you get a chance, also make notes on your player and role list about things to watch out for, like keywords and blocks.
Goo luck!