Kaidan has to just hope Rosiante is disarming the frozen bandit-- he's busy watching out for any others that might be coming up. There is enough fighting going on in various places that the bandits are spread out, but he is still on the alert in case any of them notice one of their comrades frozen in place. He thinks one might be turning their way so he quickly lifts the bandit up with his biotics and throws the creature. Hopefully that's a good enough distraction for Rosianthe to finish what he's doing.

He turns back to check on the other. Kaidan sees the two bandits and Rosianthe in a stand-off with one of them. Kaidan immediately turns his attention to the other. He still doesn't use the pulsefire weapon-- though more because he still isn't sure what will happen when one is fired while the opponent is holding another pulsefire weapon. So instead Kaidan taps something on his omni-tool and fires a cryo-blast at the bandit. It doesn't freeze the bandit's whole body, but getting blasted in the face by super-chilled ice is enough to make it stagger.

Which then leaves him open for Kaidan to reave. He's still half paying attention to Rosianthe in case the guy needs back-up, but Kaidan wants to be sure the one with the pulsefire blade is incapacitated.