The Zombies in the pits are fairly resistant to the arrows and bolts your forces rain down on them. They take numerous hits, but it doesn't seem to be doing too much to them (ie: they have DR5/Slashing)... plus, it is immediately obvious that they are totally incapable of leaving. The Zombies have been impaled on the spikes at the bottom of the pits, and are held fast by them... but even if they weren't, you highly doubt that they could escape. You realize that any futher attacking like this is a waste of ammunition.
"When we fill in the pits with rubble, they will get taken care of. I say we don't worry more about them and move on. I'll send word back with one of the fighters to have the others start gathering rubble and backfilling as we go."
The first room of the tower is an entry room. A spiral staircase leads up and down, and doors lead off in two other directions... into the walls, you would assume, based off their positions. Directly opposite the entry door, another door leads forward into whatever room happens to exist on this floor.
A couple of the rogues will check the doors into the walls. If they have locks like the ones at the other end, they will rejoin the rest. Otherwise, they will both check each door for traps.
Meanwhile, the rest of the group will investigate the other room on this floor using the SOP described earlier.
The room across from you was locked, but the lock was broken, and no bar to your entry. The door, on the other hand, is stuck. Your rogues determine that the door is not trapped.
The doors leading into the walls, on the other hand, are both locked and trapped.