How long should a baby be laying down all day to encourage rolling over?

How many hours of floor time should a child have (tummy and back) Any suggestions? Still waiting for DD to roll.

Re: How long should a baby be laying down all day to encourage rolling over?

DS hated tummy time. we did it for a few minutes here and there each day. if he got really upset we stopped. so maybe a total of 15 minutes a day? way less than recommended.

once he learned to roll, we did it more and more. he was rolling belly to back at 3 months and back to belly at 5 months - but even then he would "forget" how to do it every so often.

now he is a rolling machine