How many people within hearing range will know what a roaring Dragon sounds like, though? As a magic effect with a finite AoE, the roar should not be that loud beyond the edge of its range.
There are a lot of Devils spread over a good sized area, so our options to affect as many of them as possible are fairly limited.
Summoning, even a 9th level one to Summon a Demon, would not be too helpful right now, IMO. Now when we get ready to depart, leaving some Demons behind to make an obvious attack on the temple might not be a bad idea.