FWIW, I keep about 25 rats(pets only) in the same room as all of my Ball Pythons and never once have I been bitten if I smell of rat. None of my 43 Balls recognize rats as food. Now if I take them into the living room where the mice(I feed mice only to the Ball Pythons) are located, they can get a bit more "aware".

One word of caution though, since you are keeping pet rats, I would not bring in live, unquarantined rats. They can put your current girls at risk from viruses such as Sendai, SDA, external parasites such as mites and lice. I would either feed mice or feed f/t rats, much less risk of bringing something unknown into your current group.