HI Shades,
Sorry to take so long to reply, especially when you're worried about Alyssa.Internet problems here.
There's two babies in my baby playgroup that are slower than Poppy at the rolling and moving around. One is rolling over now, the other not. The second one can roll on his side, but he's not too impressed by the view so he just flops back onto his back.
Poppy has been rolling over for weeks and weeks but she's really not interested in moving around. I thought she'd be crawling pretty quickly, given how fast she mastered the rolling over but she doesn't seem interested just yet.
I don't think you should worry too much. I remember my mother was very stressed that my sister was developmentally delayed. She was very late in walking and was taken to a special doctor to be assessed. But now we know that was just an early sign of her very stubborn nature! She's a physio now.
Try not to worry but keep an eye on it.