This place is absolutely terrific.
I've been visiting here since we moved to the beaches and, coming from some of the more expensive/trendier places around Trinity-Bellwoods, I can say that I far prefer Roma over any of the other barbers I've seen in the city. At Roma you're going to get a classic experience: the place doesn't attempt to be trendy and, instead, you get an exceptional cut at startlingly low prices.
Here's how it goes: once the single chair is free (expect the wait to be about 30 mins per person ahead of you) you'll give a very brief explanation of what you want. And then you're just let alone as he does his work. Don't come here for extensive or extended discussion. Instead, use the time to just relax. After the initial cut is done he'll straight razor the back of your neck, then finish up with some minor trimming. And at the end you're going to get a shoulder massage.
And all of that for about $13 (cash only). No joke.
It's pretty normal for people to tip 'big' given the low cost of the cut. Given how expensive other places tend to be in Toronto you can afford to give extra since you've saved so much on the cut itself.
If you're in, around, or can easily get to Roma you should. The wait is going to be well worth it. And remember to bring cash!