So many of players didn't use grappling hook for once in game. At most prisons you just don't need it. There's a reminder that grappling hook is very good item that can spice (not sure about that word [google translator]) your own prison! It's not really hard to get it, you need only 70 IQ and items. These items are: 2x crowbar, ducttape and rope. For me it's a lot easier to get crowbar than it was in The Escapist.
So arm yourself with one of those powerful tools and explore the roofs!