We bought a sleep curve mattress for my older son and it helped a little but he is now near 2 and still has a flat bit- we probably notice it more as his parents as not that obvious with his hair grown in x
If baby still not rolling: https://www.facebook.com/share/g/16JqJFifqJ/?mibextid=wwXIfr
I bought a pillow from John Lewis that has a dip in it to use supervised during the day and has been helping