my baby is premature her birth weight is 1.5 kg now she is 5 month old her weight is 5.2 kg is it normal? she does not roll over so when we start her to sit with support?

A. doesn't not roll over yet no worries soon baby will to encourage give tummy time massage well around 3&6 months baby roll over and at 6-8 months baby will start to sit to encourage you can use Babyhug booster chair check the attachment for different milestone