my assumptions here are guided by my undergraduate experience at UofT. The way I view the assessment is by looking at how large and supportive the alumni network for Rotman is. The UofT undergraduate alumni network is not very large or supportive, Rotman may be different, but if the vast majority of MBA graduates stay in Canada, you will not be able to rely as well on that network for helping you find the job you are looking for (you also need to review what major industries and businesses graduates go to).
My feeling (because I am also looking at Rotman) as an american looking to work in america, is that I would prefer to go to a top US MBA program than one in Canada. The network and notoriety of these schools is such that I would have a leg-up with a top-5 US B-school than the top Canadian B-school; and really if you're going to spend 100K+ for B-school plus the opportunity cost of a full 2-year education, be sure you're going to get exactly what you want out of it.
