Rolling as a milestone

I was reviewing some communities on Circle of Moms tonight and noted a lot of discussion/questions on rolling belly to back and in what time frame.
It is an important milestone as it is the first time that most babies actually get to change their own position at will. It normally occurs first by accident as a baby lifts a rather large head while on the belly and the weight of the head takes them over onto their back. We lose this accidental occurence now since many babies spend very little time on their bellies.
Belly time is important for strengthening shoulder, chest, neck and back muscles as well as for this  important first milestone of independence.
One can encourage the rolling by placing the chest roll made with 2 receiving blankets and placing it at the belly button level. This tips the baby forward and their instinct is to place the hands out and prop up on straight arms. As they get stronger, remove the roll and see if they can do it themselves. Rolling should happen independently soon after.