do i need to spay the bottom of a jelly roll pan then spray the parchment paper

I find that spraying the pan before adding the paper helps hold the paper in place, then just a light coat on the paper. But make sure to spray the un-papered areas well

Yes—As a responsible baker please spay the jello roll pan. Otherwise in 6 months you will have many unwanted Hoho’s running around. (sorry could not resist – I know fixing typos on hotline is impossible)

It depends on what you are making, the size of the jelly roll pan and the sheets of parchment. If you are baking cookies, you don't have to spray under the paper. If you are making a genoise (sponge) layer, and the size of the parchment is slightly smaller than the pan, then you would want to spray the pan, so the batter doesn't stick around the perimeter and to the sides. If you are making meringues, don't spray either.