K finally is a proficient back-to-tummy roller now, though she only seems to roll to the right. And she hasn't gotten tummy-to-back, which both our ped and our baby app said usually happens first. This has led to lots of frustration and whining this week. This mama is exhausted! How long did it take your LO to "get" how to roll back the other direction, instead of screaming because he/she is stuck?