Louise - if you have squared your blocks as you do them, before joining individual blocks, you shouldn't need to actually square up the quilt top. How are you going to do the actual quilting? Free motion, or are you sending it out? Do you know for a fact that it isn't square? How far is it off?

I'm not an expert at that point, but I would sandwich and quilt it and then see if it was still off any. And yes, you can use a jelly roll for binding - given that the jelly roll pieces are about 44 inches long, you will have a couple different patterns on your binding unless you have a whole lot of the same pattern in your roll.

Someone else (with more experience) jump in here and save me!