those're all good sources... if you're looking for a med-student focused EM text, however, Hamilton's "Emergency Medicine: An Approach to Clinical Problem-Solving" is a pretty good start. not as dense as tintinalli, and about 1/10th the size of rosen...
then again, the pocket tintinalli is also pretty good. good luck on the rotation.
On a practical note, I would just review the differential for c/p, ab/p, and headache. You'll be comfy with at least 60%, if not more of the cases that walk through that door. I was told this by an ER att, and she was right on the money. I just opened harrisons vol1, and found the typical presentations part. It's a hell of a read, but complete.
EM Secrets
Hamilton
Tintinalli pocket
E-mail Resurrection and try to get a copy of Dr. Christo's EM student rotation/Intern guide (Pure Gold)
ACLS pocket cards