I would just air out the enclosure and/or disinfect it. You could also just replace the bedding around where the rat was sitting on.
I have never had a freshly killed rat smell. Not the day of death, nor the day after.
I don't feed F/T or P/K stuff to my snakes, but I do feed my ferrets whole prey. I can leave the prey in their cage for 3 days straight before it starts smelling nasty, then I toss it. (some of the ferrets won't eat freshly killed prey and only prefer it if the meat has been sitting for a little bit)
But its also not in an enclosed warm cage and I also have a fan circulating the air so it's just stagnant.