If you want to prioritize playing together with your friends in the same city, I say go for that and work out the roles later when you unlock airship access to other cities. You can’t start as a rogue anyways, so that person will also be leveling another job at first, in addition to the one who will eventually take over as healer. Getting at least two classes on everyone so you can mix and match is never a bad idea, IMO it keeps gameplay fresh especially at low levels.