Actually, I do make rolls, I just don't put them down for surprise. In cases where surprise can be negated, I give spot or sense motive checks opposed by certain skills; typically bluff or hide. If you have done something simple to try to avoid surprise, you can still be surprised, but you get a big bonus, like Raisa thinking Jackal was above the doorway and he was; she got a +10 to her spot check. Sadly, like with Raisa, even if you avoid getting surprised, you can still lose initiative.
Otherwise, it's a simple opposed roll. Kevin got a great spot check to see Jackal there; a shadow hiding in a shadow above the door.
Anyway, a good haunted house theme is supposed to surprise you over and over and over...