When I was in Physical Therapy there were exercises to help turning in bed.
While lying on your back with your feet together - slide your feet toward your butt to raise your knees in the air.
To roll left - slide your left hand under your left ear - swing your right arm across your body to the left as you roll your hips and knees to the left also
To roll right - slide your right hand under your right ear - swing your left across your body to the right as you roll your hips and knees to the right also
Having a pillow under your head may help - you can also put a pillow between your knees
They had me repeat 3 times each side a couple times a day