True Patriot
Sanity is subjective

Size, 4 x8 is the minimum I would recommend for any chicken. Recommend is 24 sq ft for 6 birds. More space is far better than less. It has to be big enough for you to comfortably access for cleaning and maintenance. Mine is 4x8x 4 high, (8 standard size chickens) to build it again I would double that. Especially if there was a chance my flock would have to be confined in incliment weather.
For the roost, as long as you can make it and still fit in the coop. They like to bunch up usually, but space available reduces picking and arguments. Make sure the roost is higher than the nest boxes. If not they may tend to sleep in the nest soiling your eggs. Two nest boxes should be fine, they will most likely all use the same one. If you build the nest boxes inside, a roof at an angle steep enough to prevent landing on will also help keep the nests clean. There's lots more information in the coop and run section. Best of luck