The more advanced version of Artillery, Rockets trade higher damage and a much larger range for lighter armor and a more restrictive movement type.
Usage
Like Artillery, Rockets are Indirect Combat units. Rockets possess a much higher range of attack compared to Artillery, but also have a higher minimum range. While Artillery are only incapable of hitting units adjacent to them, Rockets may not hit any units within two spaces of them. As such, Rockets need to be more carefully placed in formations, as Rockets placed too close to the front lines may not be able to hit certain units. In addition to higher range, Rockets have higher damage potential compared to Artillery, being roughly 10% stronger offensively on average. On its own this is a small boost against most units, but this allows Rockets to much more reliably wipe out Infantry in one attack, exposing more valuable enemy units to attack.
When placing Rockets, care must be taken. Their poor movement type means Rockets will be very difficult units to move quickly off of Roads and Properties. They also have weaker armor than Artillery, taking high damage from even Infantry attacks. Combined with their minimum range, Rockets work best with at least two other units acting as a buffer to keep it protected.
Fighting Against
Much like Artillery, Rockets are defenseless against Air units on their own. B-Copters may sit within their range of fire, attacking units with impunity, as long as there are not any anti-air units in the vicinity. Tanks may also move further than Rockets can shoot, but only if there is no obstructing terrain in the way. Rockets are severely damaged by just about any unit that can attack it, so one may take advantage of poorly defended rockets by getting an attack in, but this is only wise if your units will not be left out of position as a result.
Most Ground units are much faster than Rockets when off-road, so one can easily shift the front away from an area that a Rocket unit is contesting. If there are a high amount of Roads and Properties, Recons may travel from far beyond the Rocket's range and deal heavy damage to it, despite being a fraction of the cost.