Flight Crew Instrument; Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP)
Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter Weather / Turbulence
Flight Crew Overcame Equipment Problem
Aircraft
During descent on the ANJLL4 arrival; the Captain (Pilot Flying) used the speedbrake lever. As the lever was extended; the aircraft started an abrupt roll to the left. It was confirmed via the synoptic display that the spoilers on the left and partially on the right were not extending. The crew extended the gear to slow the aircraft to the ATC requested speeds during approach as there was no way to slow without properly functioning spoilers.  Aircraft malfunction. Heavy rain in ZZZ could have frozen the controls in cruise flight.  Examine each aircraft to make sure water intrusion doesn't happen.
B767 First Officer reported uncommanded left roll when extending speedbrakes.