when did 31weeks baby call roll over

A. Hai good afternoon !! Babies generally roll over by 3 -5 months,few babies take time around 5.5 months due to delay in achieving milestones. Give tummy time daily - Place a blanket or mat keep baby on tummy side for 10-15 minutes this helps in holding neck,roll over,crawling ,strengthening abs . If you observe baby is not rolling even after 5.5 -6 months,then need to concern ,consult developmental paediatrician or paediatrician on this.