The person usually continues to roll to their side when the motion is started by the carer. Once the arm is hooked over the bed rail, they will probably hold still for a few minutes when asked to do so. The person can assist with dressing by rolling, holding their arm over bed rail, and following the direction to "hold still."
Transfers to shower beds or tilt-in-space chairs are easier when you start rocking motions to sit up in bed.
When a tilt-in-space chair is propelled over toilet / shower commode, the person usually cooperates by holding still.