You messed up with the word "repeatedly". Leveling Roulette is great IF you are getting the bonus for running it once that day. Just like all the roulettes, they don't pay out if you run it more than once a day.

Also, the exp gain will vary. Since lower level instances will give less exp than higher level ones (the bonus at the end should be similar, though), sometimes you get less payout than others. However, landing in something like Ifrit means you are getting the roulette bonus for like 45 seconds of work, so it's MEGA efficient.