rolling from back to tummy

Anyone's baby rolling from back to tummy yet? My LO will be 12 weeks tomorrow and is SO close. She's constantly rolling on her side and almost to her tummy but she gets stuck laying on her arm and then proceeds to bury her mouth in her arm. It has me terrified because she is starting to do this at night too. And although she can roll from tummy to back she hasn't fully mastered it yet!  Anyone else? Any suggestions? Are you rolling your babies back to their back when they roll? I know rolling over is inevitable, I was hoping for a little more time before it happened. So worried about SIDS.