I agree with mrgmfoster,as a pit bull owner I can say one thing Rory has tought me is that force is NOT going to work with her. These dogs demand respect, treat them as you wish to be treated. By rolling her over like that she will feel helpless, cornered and could lash out.
Now I told myself I was going to stay away from this thread but you asked a question, I'll answer it in my best opinion and experiences, please take no offense.
Now while I think its great you took in a rescue I think it stinks that you have doubts right off the bat but obviously your heart is in the right place. By ownng a pit bull it is your duty not to neglect it or it will have behavioral issues and that gives ALL pit owners a bad name.....not what we need right now. It is your job to stand up for your dog, love it unconditionally as it will you, yet stay educated and aware of its limits and or issues as with all dogs. Good locu, please keep us posted