A dungeon boss will come into play as part of next round's spawning phase once either all spawning points are destroyed or the Power Gauge reaches it appropriate level. Once it comes into play, spawning points no longer spawn monsters. So, in the round that a dungeon boss is being spawned, could the Consul spawn other monsters before and/or at the same time as the dungeon boss?
Don't have the rulebook to double check this right now, but I believe he spawns in any room not occupied by a hero. Although "rooms" are not tiles, so that's hard to figure out too. One guy here differentiated tiles into various rooms and his pdf of how he does it can be found here:
Also, I think I read that another person here was just spawning the dragon at least 6 squares away from any hero, instead of dealing with the whole room confusion thing, and still keeping the dragon from spawning right no top of everybody.