Hey, I realize this is a month from when you asked the question, but I facilitated a group of three, so I can maybe help if it's not too late!
1) If you're playing in person, it should be as easy as just handing out the role sheets face down. Digitally, I couldn't think of a way to do it, and just accepted that I was going to know who had what roles. Maybe if you had somebody not playing who was willing to divide them up and text out assignments, or drop spoilered messages in a Discord that people can click and claim?
2) When I facilitated, I checked if anybody wanted the second role, then took it for myself since I was more familiar with the game. Some people love playing multiple characters, some hate it, so that's probably the best way to handle it.
I DO think the game is playable with one role missing, but it may mess up the math a little bit.