My dormitories only allowed fish in small tanks, nothing that could climb out of its enclosure.
Of course in breaking the rules I chose a pet that was the most likely to escape its enclosure. This risk was made more imminent by my experience, I was a first time owner.
The consequence of my 3 month old cornsnake ending up in my Hawaiian native RA's room was... a very freaked out girl, a 1,000 word essay assignment, and a $15 fine (not for having the snake but for taking up a 5 minute slot of the disciplinary lady's time).
Good luck with your roommates! Only thing.. make sure you know someone outside of the school's living situation who would take responsibility for your pets if you were to get caught with them. I'll admit though, my friend who smuggled in a frog was much more successful than I at remaining undetected.