Please help with Rokinon 7.5
Also, is there a way to make the camera magnify the image on the screen to assist with focusing? I've looked in the manual focus, but can't find any way of doing this.
There is always a way to magnify the live view in manual focus mode. Without knowing what body you're using there's no way to tell you how to do it.
This info will, of course, be in your instruction manual, and you could google the info pretty quickly.