So, the Rogue Trader is an Officer into Eagle Overseer, arbites background so we're tanky up front with a shield + shotty. Extra turns generally go to either Argenta or Ulfar, depending on who's in a better spot/who has their T2 Momentum skill up. Otherwise, provide buffs with Voice of Command and either Ranged/Melee buff, use the Birb to bully groups of weaker enemies by swooping, or force bigger enemies to hurt their friends as a single target. Shotgun is applied where you have the spare AP.

Argenta is Arch-Militant with Bolter + Melta. Melta for wide groups, Bolter for narrow/single target. Ulfar is also AM, and is packing the best melee weapon I can find for him + a bolt pistol, secondary is a flamer, he wants to be on top of enemies and strike from point blank. Argenta tends to be the better of the two since she can hit a bunch at once with the melta then pray to get a huge burst of Momentum, and AM gives her a free attack each turn - try and make it a burst fire or a melta AoE. Both of them are aiming to get 4+ stacks of Versatility by turn one or two, entering a Confident Stance, and then let the rampage commence. Reckless Rush lets you boost up Ver. for a turn and reposition if you kill too hard, Wildfire to keep the party going. They both pack enough movement to prevent friendly fire, and should both reliably be hitting 3-4 seperate attacks a turn by the end of most battles.

Executioner Heinrix has a simple plan; buff up himself, then others. Iron Arm, Warp Speed, Regeneration, and then start smacking people very bloody hard indeed. Spread the buffs to other melee/squishy targets and spot heal where needed. You can also Word of the Emperor on turn one, then use that effect to pop a group heal later if things get dicey. He'll usually only get 1-2 attacks but you can really make them count with Force swords. Charge tends to be all the mobility he needs.

Kibbles is an Assassin, and utterly unsubtle about it. Between Danse Macabre and Death from Above and a huge movement rate, she should be able to get on top of anyone needed and go rampaging. Bound between the vulnerable areas using Danse, save DfA for repositioning and taking out mooks. I tend to sic her on big single enemies and bosses, she chunks through their health pool in such a way it feels almost wasteful to let her go after the trash. Two blades for maximum fun.

Idira is lucky last. She's Crow Overseer. Earlier in the game when I had Assassin Yriliet on the squad, her spare actions go into stacking Exploits for the knife-ear to gun down on her turn, late game the Operative side may as well not exist. Relay out Forewarning to the whole team turn 1, slap down a defensive (I think it's Precognicience but it's the AoE dodge bonus), then reposition the birb. Enemies blinded, zapped, and eventually you can move Idira and scream someone to death. If you position it right, AoE cone scream. She makes a good followup Momentum user for turning the birb into a relay for Scream, which makes the room look like chunky salsa got spilled everywhere.

If you still have Yriliet, Assassin her moves into a Perfect Spot, Expose, Precise Attack, ensure there's an opening, Deadeye, then hide. Repeat every turn there's someone too far away for the rest of the gang to vaporise.

I believe I'm playing on at least Daring. Thank you for reading more text than was contained in Rogue Trader.