Don't know where you can get plans, sorry (tho I'm sure there are some out there somewhere), but I will warn you that I have read almost uniformly negative things about roll-out nest boxes. People who have them tend to say that you can't keep 'em clean no matter what, and it can be awful hard to achieve enough roll that the egg leaves the box but not so much that it breaks.
From his experience, it sounds like it works. I've made one for my tractor/coop but my hens haven't come into llay yet so I don't know how successful they are yet...