I finally got off my lazy butt and confirmed how Rollout works. I used a Sharked level 38 Rhydon against a level 100 Chansey. Here's how it went...
Rhydon used Sweet Scent a couple times to keep Rollout from missing; Chansey absentmindedly Pounded to pass the time. Then the Rolling body of Rhydon started up. The damage progression on each hit was:
15 -> 31 -> 60 -> 123 -> 224
Then Rhydon used Defense Curl and tried again:
28 -> 64 -> 119 -> 243 -> 493
This means that Defense Curl doubles the power of Rollout for each of the five turns. Now, another question on the subject was whether a 960-power Rollout (fifth turn w/ Defense Curl) would produce very little damage if Hard Stone was attached, due to the 1023-max rollover. I attached Hard Stone and ran the tests again. Without Defense Curl:
14 -> 27 -> 59 -> 121 -> 229
31 -> 63 -> 114 -> 222 -> 495
This proves that rollover isn't a problem.
However, a new issue is raised; notice how there was no discernable increase in damage when the Hard Stone was attached than when it wasn't. Does this mean that Hard Stone doesn't affect Rollout?
"The Holocaust was an obscene period in our nation's history. I mean in this century's history. But we all lived in this century. I didn't live in this century."
-- Al Gore