I haven't tried it but I'm having a hard time believing that it would make any difference, other than muscle recruitment.
Well, I dunno. I've thought about it two different ways, but I've never tried it either.
On one hand, you're not actually
going anywhere, so there's no power used to move weight up the hill.
On the other hand, if you just sat on the rollers, I think you'd roll off the back if they were inclined. Which seems to point to having to do extra work against that.
I dunno.