Here is a video of Mary rolling - well close to rolling. Henry is cheering her on and if you watch closely you see her get this big smile every time he talks to her.
Yes, Henry is mocking my baby voice in the video.
We have Mary's four month appointment on Friday and I am hoping I can tell the doctor that she rolls over. If I remember correctly with Henry, he rolled over the morning of his four month appointment, so maybe she will repeat.