I've heard everywhere that pine is harmful to snakes, I definitely wouldn't risk putting your rats on it. Also, if you have snakes that have good appetites, if they smell the rats they may become a bit more feisty and aggressive than usual. If your rats are very well contained, I'd try it, but especially now that breeding season is over, my balls are more piggish and nervous than usual so I'd try to put them in another room.