Challenger 650 Captain reported during descent with the Autopilot engaged; the aircraft rolled slightly right when they deployed the flight spoilers; and the Autopilot corrected back to level flight. Due to icing conditions they decided to divert.

Narrative

During descent and about to enter icing conditions the pilot flying deployed the flight spoilers while the Autopilot was engaged. The reporter believes the flight spoiler selection was the first or second setting. The aircraft did a slight roll to the right and the Autopilot corrected left to wings level. The pilot flying stowed the flight spoilers and the reverse occurred. The crew discussed the situation and attempted to redeploy the flight spoilers to see if that was the problem. The crew then attempted to slowly deploy the flight spoilers to the first setting and the roll right occurred again with the Autopilot correction back to level flight. There was no indication on the annunciator display for the flight spoilers. The flying pilot selected the second setting and the roll right correction left to level flight occurred again. The flight spoilers now showed the first setting (arrow) deployed on the right with no indication on the left. The flying pilot stowed the flight spoilers; and the reverse occurred again. Now having confirmed the issue the crew discussed diversion or landing at planned destination. Due to close in high terrain at ZZZ1 and icing conditions during the descent the crew decided to divert to ZZZ. ATC was informed of the same. The crew then informed ATC that priority handling was necessary. During several handoffs to ATC the crew had to repeat the nature of the problem; number on board; and fuel on board. This was distracting to the crew and not optimal. However; ATC later offered a longer runway than had been planned once the nature of the problem was understood by ATC. This was helpful information; but not necessary; because the planned runway (ZZZ Runway XXL) was 12;000 and sufficient to capture the 1.25 QRH penalty. The crew decided to not select the flight spoilers on landing. Suggestions: The auto throttles in aircraft have been deferred since Day 0 and this added unnecessary workload to the crew during the problem. The aircraft has been overnight at numerous maintenance bases since Day 0.