I think I might have found a solution to my role selection dilemma - a rondel with a twist! There would be 6 or 8 spots (depending on the number of players, I might double up on some of the actions), with each player able to move 1-3 spaces on the rondel each turn. The catch is that if you ever catch up or land on another player as you take your move, they are able to take the action you're taking as well!
So there would be a balance (hopefully) between setting up your strategy, which would probably revolve around 2 or 3 actions that you would want to hit as often as possible, and not trying to give your opponents free actions. And if you do have to give them free actions, choosing actions that are much more advantageous to you would be a good tactical play.
I've also decided to combine the contacts and ships deck to one deck, and changing the Central planets ability to playing a Contact card from your hand. I'm slowly working through all the cards, half of the ships are done so far (still most of the planets and all of the contacts to do). I'll put more information on the ships and their abilities up here once they're done.