Not entirely, I may be wrong,
but I would make it like this:
You have your "Rolling Mountain" biome, then you add several (Maybe not just one or two. But like 5-6) biomes (ID at the virtual Biome range, to conserve true Biome IDs). You let them Extend the First Rolling Hills biome, and only change the Height in each biome, maybe some slight variation in the smooth Radius, and set them as Isle in the Rolling Hills main Biome.
The Height in each Isle is really high. They should be allowed to reach very high. But the twist is:
The actual Height will be limited by the smooth Radius. Because the SmoothRadius will be bigger than most of the Isle Biomes.
In Theory with these settings you should get an awesome result. (Not Yet Tested)