Has your trainer seen first hand your rottie's reaction when on lead around other dogs? Once she has seen what your dog's behavior is like then she can best recommend what tools and techniques will work best.
Don't be afraid to try and find another trainer if your current one isn't helping much.
On a pinch collar you would be giving your girl corrections if she started showing signs of acting up while another dog passed. You wouldn't wait until after she has already started to react, it is all about preventing her from escalating. Watch her like a hawk and learn to read her body language. Put her in a sit stay when another dog is passing, and if she tries to break her sit you can give her corrections using the prong.
Some dogs do better with different techniques. There are so many different things you can try to be doing with your girl, I am sure others will chime in
Thank you for rescuing!