We had our 4 month check up yesterday and we saw the nurse practitioner for the first time. She asked me if LO was rolling from her tummy to her back yet and when I told her she was not she seemed really surprised. She told me she should be doing this by now. We do tummy time several times a day but she gets angry and would rather be on her back. She rolls from her back to her sides but not from tummy to her back. Is this a problem?? Anyone else not doing this yet? I don't remember when my son was doing it and her reaction has me concerned.