What age do babies roll?

What age do babies roll from front to belly? But I mean when they roll and then push themselves up on their hands? My son is 5 months and he is flipping over every time and he pushes himself up. My friend said that he should be doing that at 3 months wtf. Surely not? I don't care if he isn't quick at learning he's healthy and that's the main thing!! Always someone making comments ah!