6 month tummy time?

How can i encourage tummy time at 6 months? My son still isnt rolling back to tummy and isnt consistently rolling from belly to back. He does roll but just not every time and sometimes cries for me to helo him. He sits independently and gets in to crawling position already so its difficult to keep him on his tummy to master rolling. Any ideas? He prefers to sit and play now and hates playing on his back and tummy. I still try regardless multiple times a day but im not going to let my kid scream and cry just so he gets his tummy time in. We have talked to his doctor about him not rolling at 6 months and she isnt super concerned yet as all his other milestones are either spot on or advanced.