For us - broadly similar to drivers, I think - the main rostering restrictions are 12hr maximum shift length, minimum 12hrs rest between shifts, no more than 13 days worked out of 14 and no more than 72hrs worked in a week. The base roster will be nowhere near as demanding as that though, so it's your choice how much you push yourself beyond that (a week of, mostly, twelves really can be hard going).
The base roster works out at a weekly average of 35hrs excluding Sundays, but some weeks will be more than that and some less. A four man box, open continuously, will go up to an average of 41hrs with Sundays included, but that's the 'worst case scenario' in terms of committed hours. I'd never ever recommend relying on overtime, but there does seem to be loads of it about in most areas, as the other Tom says. I've worked at least one rest day most weeks, quite a few Sundays and occasional twelves (instead of my booked 8hrs), and even at that been offered quite a bit more.