TM, if you roll to 30 degrees and then only pitch you'll eventually end up pointing the other way with 120 degrees of bank on.
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You may have misunderstood the use of the specific CWS mode in the 737 autopilot system. With CWS engaged the pilot controls the aircraft manually through the AP system. If you roll to 30 degrees angle of bank in CWS mode and the pitch attitude is correct, then on releasing the wheel the aircraft maintains 30 degrees angle of bank.
Extract from the FCOM as follows: "With CWS engaged, the A/P maneuvers the airplane in response to control pressures applied by either pilot. The control pressure is similar to that required for manual flight. When control pressure is released the A/P holds existing attitude".