Roy got a WONNNH!! when he went toward the dead end, so if we stipulate that teleportation is happening, it is happening. Ergo, the dead end tunnel is the tunnel where Team Evil is, Roy is correct.
Now, question B: does "bypassing" the trap leave you in a tunnel in the "real" dungeon, or does it also teleport you, with less effects, into the "real" (yes, I'm assuming, shell game and all) dungeon. The answer, in my humble opinion, is does walking down the tunnel yield a bunch of branch points where you can join all the other doors?
That's my idea, 5 Quatloos.