If you are NOT on a lease and you did NOT pay first & last the standard would be 30 days. However, it depends on the agreement you had with you roommates, if you even discussed it.
30 days is suffiencient under the circumstances but I'd say it depends what kind of relationship you have with them and what kind of relationship you want to maintain with them.
Unless you know there's people lined up outside to take a look at the place, I wouldn't recommend NO notice
I wouldn't worry about giving 60 days unless you really think it will create a problem. There really is no guidelines in the Tenant Protection act that outlines shared accomodations. Like I said before, it's completely dependant on your current relationship with them and the relationship you may want to maintain after you move.