What should I get?

[MartinD]

You can try and then observe the snakes behaviour, here are 2 responses from another site....

From what I've observed, every snake in my room (6 snakes) had no change in their behavior when I went in to get them out of their tubs. The two closest to my rat were my BCI and Kenyan Sand boa, but every time I took them out they were just fine and acted very calm.

With one rat, I'd doubt you'd notice any difference. When you start increasing your numbers and they really start putting off a noticeable scent, then you'll be able to get a better idea.

When I first moved my rats in the same room as my snakes so many years ago, I thought that I'd at least notice a touch more cage aggression from the snakes, but so far, so good.