This was posted to the AE Mail-List, which I don't really read much anymore, but it's a great resource. This one caught my eye, because the West Michigan After Effects User Group is going to present a little roto at the next meeting. I can't wait to show everyone this tip.

From Alex (aenhancers.com): "I'm on a pretty huge roto job for the moment, and as I was on my 356'th frame of my 5th sequence, I was starting to have very achy eyes. It kind of sucks that you can't make your mask vertices bigger in AE, and zooming into the comp doesen't make the mask look any fatter. So I contantly had to move very close to the screen to see what I was doing, mostly when the mask was on top of a color similar to its own.

So I remembered the mac os X built in "Zoom" function. Go to the system prefs>universal access. There you can switch on a "zoom" function that lets you zoom into your screen. It is a pretty cool tool for all sorts of purposes, but in my case, using a combination of zooming in the comp in AE and zooming in the screen in the OS, I got a big looking image, with a fat mask I could still see while sitting back in my chair, instead of nose against the screen. More precision / more comfort. (Command+Option+8 should get you there).