I wouldn't expect to roll in a single day. Very few people do (I'm told) unless they're in great shape and get a well-fitted boat their first time, plus stay calm when you flip in moving water.
I took the South Platte course twice. The first time was after the single-day on flatwater, and I swam 3 times. The second time after practicing, but still without a roll and I didn't have to swim (one t-rescue).
South Platte is, from this beginner's perspective, a very good first run. The drops aren't complicated or long (there are two doubles on their lesson, but they're very doable), and the flatwater afterward is great if you have to swim.
Plus, there's no reason you should HAVE to swim on their course because the instructors will be right there for a t-rescue. It's just a matter of nerves.