I'd be interested to find some of this out myself. I've a mate from Ballymun who is a big Bohemians fan and their (or his anyway) mortal enemy / derby is St Patrick's Athletic. Looking at Google maps that's slightly northside v inchinore.
Edit, reading a bit seems Bohs v Rovers is 'the" derby.
Edit, reading a bit seems Bohs v Rovers is 'the" derby.