Motor delays

[sharishu]

My 15 month old son is about 3-4 months delayed. He goes to physical therapy, and is coming along nicely. Slowly but surely. The one thing that concerns me is that he just does not roll over (to his back) to switch positions independently. He CAN roll over, but just does not. He starting (slowly) to practice pulling to stand... but I still need to put him in the sitting position. Anyone out there go through this with their baby? (Otherwise, he seems to be developing nicely, on the low end of 'normal'... and he's cute as a button! ).

Shari