We were learning about angular momentum in class today, and although it sort of makes sense, it's much harder for me to think about than linear momentum. So from what I can tell:
Angular momentum and linear momentum are conserved separately: i.e. they can't be converted to one another to 'compensate' for an apparent drop in net momentum
Every torque has an equal and opposite torque
Assuming those are true, consider the following scenario:
A disc with a rocket attached tangentially applies a thrust and thus a torque. The disc will go and fly in a circle, and ejects gas molecules in a circle, so linear momentum is balanced. The disc also has angular momentum, but the gas molecules all only go off in straight lines, so where is the torque opposite to that applied to the disc?