I think a lot of roles are pretty fluid in Zero-K.
Good players know when to change role or pick a role that seems to be lacking when players choose start position and place their factories before the game starts.
It is also map dependent and player count dependent aswell as skill distribution dependent.
Like if a player is experimenting with some playstyle they haven't tried before, their effectiveness in that role will be a lot smaller than a player that perfected that playstyle.
In some games, you can do fine without having any fighters in the air, and in some games it will be crucial that you have fighters in the air.
Like for an air player, there are arguably like 4-6 distinct subroles that is impactful to what your teammates or enemies are doing:
1. Fighters or no fighters? If the map is small, it is arguably better to make some ground AA to deny enemy fighters and let the airplayer just bomb the enemy.
2. Thunderbolt suppression. A Thunderbolt is kinda bad if there are no fast units on your team to capitalize on chasing down slow disarmed enemies or if the enemy is all raiders while your team has just slow units.
3. Pheonix to burn down groups of enemies and killing groups of raiders.
4. Single target reliable damage with Ravens or Magpie.
5. Rushing out Likhos for high survivability and killing shieldballs or other groups of enemies or high value targets. Will easily fail if there is not enough AA on your team and the enemy has Swifts.
6. Forcing out AA on the enemy team and switching to ground units once there is too much enemy AA on the field.
How many clear roles are there even in teamgames?
1. Airplayer/gunship players both have the same impact that they can be strong if left unchecked but is countered by AA.
2. Frontline player. Most players should be doing this.
3. Economy player. It can be nice to a have a few players dedicated to this but it easy to switch to air or the frontline later.
What alternative roles are there?
Is support a role where you make units like Racketeer or Placeholder?
Does a shieldball count as a role?
Does rushing a heavy count as a role?
Does raiding count as a role?
Is cloaked bombs a role?
Like if you want to rush out a heavy, that is more about teamplay rather than a role, and if you tell your teammates that you are rushing out an expensive unit, they will be a bit more careful with pushing and wait for the heavy unit to get finished and push with it or provide support for it.