>>38315507OP here.
Yeah, even by meme standards Defense Curl + Rollout didn't work. When it didn't end up missing they'd just switch into something with a x4 resistance and kill me back. I also tried a Thunder Wave + Curse set, but that worked far better for Registeel, so I decided to try working with Regirock's natural bulk and use Counter: and it's worked beautifully so far. Mega Lopunny with HJK has done only around 56%, which activates sitrus and then get OHKO'd back by counter. It's pretty fun.
I've also tried the Gigas set in RU, which isn't the most popular tier I know but I thought would be an interesting playground. To my surprise, he's actually carried a few games and at least twice I got Regigias to pull off a full sweep. It's pretty awesome to pull off, however unlikely.
>>38314565gr8 b8 m8