Air carrier Captain reported aileron trim malfunction during approach resulting in an uncommanded roll. Crew regained control of the aircraft and continued to a safe landing.

Narrative

I was assigned to work flight as Captain (Pilot Monitoring) with First Officer (Pilot Flying) from ZZZ1-ZZZ. The flight was proceeding as normal until approximately 5 minutes from ZZZ at 6000MSL on a right base for Runway XXR in straight and level flight. Approximately 5 minutes from ZZZ while the autopilot was engaged in Heading Mode and Vectors to Final activated; the autopilot began an uncommanded roll to the right. The PF immediately recognized the uncommanded roll and requested 'AUTO PILOT OFF;' I immediately pressed the autopilot disconnect switch and he stated 'The airplane is still going to the right; trims; trims; trims.' At that time; I noticed there was no indication of a trim runaway as all trims were stationary. The aileron trim was activated by the PF 'Maxed' to the left and the airplane still wanted to roll to the right. No CAS messages were indicated. The PF was still fighting the airplane to maintain straight and level flight. At that time; I took control of the airplane and started to adjust the aileron trim back to the right and was able to relieve control pressure. Controls were given back to the PF and a safe landing was made. The airplane was taxied to gate and passengers deplaned without incident. The incident lasted approximately less than one minute and was resolved; therefore; an emergency was not declared. The airplane was taxied back to the maintenance hangar and an AML Entry was made. Maintenance and personnel were notified. Cause: The possibility of an aileron trim failure or malfunction.