roller is a rover type - original plan - city defense unit.
It makes no sense to me that a rover is a city defense unit. Even the name Rover implies a high movement field skirmisher.
To me, roller actually implies a city assault unit rather than a field-superiority unit; I think the name showed up in some other scifi; pirates attacking a planet had infantry and rollers, which were kindof mechanized battering ram/apc type things, that were designed to be heavily armored and punch through defenses, and then let the infantry out.
Why are melee units 2 moves but ranged infantry aren't? Doesn't quite make sense.
The Al-Lat (strength 25) comes shortly after the lasgun trooper (strength 12) but well before the lasgun soldier (strength 24).
The basic unit roles from civ work pretty well;
City defender (archer)
City attacker (swordsmen)
Anti-city attacker and anti-anti-mobile unit (axemen, crossbow)
Mobile unit A: field superiority (knight, armor)
Mobile unit B: skirmisher (horsemen, horse archer)
Anti-mobile unit (spearman, AT infantry)
Anti-air unit (SAM trooper)
Artillery (catapult)
So I'd consider:
City defender; soldier, infantry, infantry 2, al-lat
City attacker; melee infantry/shock troops. Raider, bladesman, elite bladesman, lasgun trooper, saudarkar (these units ignore city walls)
Anti-city attacker; thopter, battle thopter, assault thopter. Can't capture cities, can travel in deserts. Grenadiers.
Mobile A: 2 move mechanized units, high strength. Scorpions.
Mobile B: 2-3 move mechanized units with lower strength but withdraw chances, bonuses vs artillery. Quad, Sand Rover, Dune Buggy, etc.
Anti-mobile A: Burseg, Saudakar, Al-Lat. Anti-tank units.
Anti-mobile B: missile troopers. Anti-thoptor, anti-aircraft. Intercept chances.
Aircraft. Hornet (fighter), assault hornet (bomber).
Artillery. Maula siege.