A roof with a 4 / 12 pitch what angle do i set the mitre saw at to cut the 2 x 4

I need a mitre saw for some do-it-yourself work around the house like pergo, baseboard, extra. I'm considering a 10-inch single bevel mitre saw by DeWalt or Hitachi. Any thoughts?

I would like to build a workstation for my chop saw, but I am unsure of where to get plans. I was hoping to find free plans on the internet, but need to be pointed in the right direction.

I cannot figure out how to unlock the blade so that I can lift it out of the saw bed. It's a 1992 7700 heavy duty.