Mine was lazy, wouldn't until 6 months, he had done it a couple time around 5 but he could do it was just not wanting to so he didn't
Two months but after that he did everything a lot slower lol.
I believe 4 months. Took him until 6 to start rolling back and forth like crazy though
2 weeks he started rolling over and 4 weeks he started rolling back to front and front to back