My comparison between chiro & osteo (love them equally for different reasons) is that I'll go to my chiro when I feel like my skeletal frame is/has ceased -example when the right side of my rib cage feels tight & no longer seems to expand as easy. The relief is almost instant although I am tender for the next 24hrs.
I visit my osteo when I feel tight in my muscles, headachey or I know I've over extended my lower back/hip area. The gentle manipulation is what I need when I'm feeling sensitive itms?

I think it comes down to personal preference. I personally would be more inclined to take a baby to the osteo as I feel it's a more gentler treatment but then again I cannot imagine a chiro cracking a bubs bones!

I hope you can find answers regarding your LO's difficulties rolling over.