To be honest the random selection makes it a bit more fun and it's still just as easy. At least on normal mode. I get that people love having a set up strategy and a role for their own to follow, as to not worry about anything else, because I've done that. After a few times though I got bored of being on the outside defending portals, but now I get a chance to either tear down oracles or -blam!- shit up with a relic and actually learn the role in case I need to use it.