I personally don't keep a ratsnake, but I do have a couple of corns and a MBK. They've been fine in a sterilite, but I do feel like the ratsnake family are very interactive with their environment and benefit from a full set up.
But, if it means anything, BHB does keep all of his colubrids in racks.
I keep all my snakes in tubs fit to size, including several rat snakes, and I don't have any problem...I take the snakes outside regularly in the summer, but for the most part, they seem indifferent to their enclosures.
"Maybe humans are just the pet alligators that God flushed down the toilet." -Chuck Palahniuk