The sim probably won't react like the real thing, but one factor is that a helicopter cabin is usually a big draggy box hanging from the rotor head.
If you use pedal to yaw left, say, the relative airflow on the fuselage is coming from the right. Now the rotor head is trying to drag that cabin along while it's cocked off to the left, and the result will be a tendency to roll to the right.
The effect is particularly pronounced in a teetering head helicopter with fixed floats (ie heaps of drag surface down low, and also more forward than usual, reducing the longitudinal stability). If you yaw one way, there's a big roll the other way so it will wallow along like a big pig.