I have heard of babies skipping pretty much any "major" milestone. She may not roll over before learning to crawl but, at some point, I'm sure she'll figure out how to do it.
Also, both of my kids had 9 month check ups as a standard checkup, not as something special/extra added in to address a concern. They had different pediatricians when they were babies, and a 9 month checkup was standard for both. So, I actually think it would be strange NOT to have one at 9 months. At this age, going 6 months between appointments is too long - way too much changes between 6 and 12 months.
Anyway, your daughter sounds fine. She is learning to move around and, I imagine, holds her head up well when she's on her tummy. So I think rolling will just come along later down the road, not as much of a big deal when it does, but more just yet another way that she moves around.