Rodolphus is definitely with them when the voice booms and is ready to finally take over. However, when he watches the first of the DE's fall through the chasm he is determined not to go through and will back away to the edges of the pandemonium. This is where I hope Rabastan finds him and teaches him a much needed lesson (not that he'll be changing any time soon, but every little bit of steering helps ever so slightly). Rodolphus isn't going to actively hurt villagers. There are no DE's he cares about other than Rabastan and Bellatrix and they are here and isn't willing to die for any of the others.