The party backtracks the way they came, reaching a door you passed previously while chasing the first infected kobold. Determining that it is not locked or trapped, Rogash opens it only to discover that it is one of the many doors in the room with the black tentacles trap. This door, along with the one you first entered through and the one on the opposite wall through which you exited make three of the five total here.
There is still an unexplored corridor just around the bend from this one, as well.
So, your options include:
A: Back around the corner through the as yet unexplored corridor, or..
B: Through to the other side of this room and out one of the other doors. For the record, the lingering dust appears to have settled nicely on the floor. The torches are still lit.