Tactical observations: the Imperials look like started too close to the Orks. The Heavy Gunz on the Roks are devastating, but only have a 15cm range, so it's essential to stay out of that range. The Gunz have a 45cm range, so the frigates have to move into Gunz range for their weapon batteries to be effective.
The Imperials also should not have split their forces, if possible. The Orks are deployed in a long line and face defeat in detail. Only let one Rok in range at a time. If the second Rok is further than 30cm away, missiles will need two player turns to reach their targets, making it possible to dodge them at allowing the frigates to use their weapon batteries to shoot down the long-range missiles, if necessary.
If you keep the Heavy Gunz out of range but you are in range of both Roks, you appear to be outgunned by an average of 19 to 16 (the Roks vary from 4 to 24, combined). However, Roks are Defences, so they are very easy to hit. You really, really want to take advantage of a "crossing the T" tactic by exposing the frigates' flanks to the Roks, greatly decreasing Ork firepower. How much is this effect? Well, the 16 Imperial batteries generate 16 dice if the ships roll separately, 14 if they roll as a squadron. If a single Rok fires at a frigate head-on, it gets an average of 5 dice. Firing from the flank, it only manages to average 1.83 dice. Huge advantage to the Imperials, even though the Roks are far harder to kill. Even if both Roks are firing, that 10 dice and only 3.66 dice. It really shows the importance of crossing the T. Keep in mind that it doesn't matter what direction the Imperial fire hits the Roks from: Roks are Defences, so they always use the same column.
Of course, the Roks are going to strike with their missiles, which are likely to be devastating, but at least they're lousy at reloading!
If you really want to go toe-to-toe with the Roks and cross their T, you have a small chance of killing a Rok in a single turn and the Roks have a chance of killing a frigate (putting aside missiles). Even if the Roks kill a frigate, the Imperials are almost certain to finish off a Rok on the second turn of firing.
Again, though, the problem is those darn missiles! Each Rok's salvo will average 3.5 missiles, the frigate average 1.75 shot down, and 0.6 hit vs. armor. (This does not mean a 60% chance of destroying a frigate; that calculation requires a lot more work. This is just to get us into the ballpark.)
However, after this shot, the Roks are caught on the horns of a dilemma: if they try to reload their missiles, they can't maneuver at all (excepting their 10cm drift forward). That gives the Imperial frigates the perfect opportunity to either defeat the Roks in detail or to start killing transports. (Killing a single Rok opens up the possibility of slaughtering all of the transports on that side of the formation.)
This is not to say that these tactics are trivially easy to implement, but they do point the way to an Imperial victory in what at first looks like a very unbalanced scenario.
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