Sonic style platforms

I`m trying to create a platformer with similar style slopes as in Sonic The Hedgehog (the older Megadrive 2D titles) that make the player rotate slightly as he\she goes up and down the slopes (they are curved). This is proving quite difficult and I thought that I`d ask to see how others would tackle the same problem without mentioning how I plan to do it to see if anyone has any different ideas that could work.

Any help would be great,

Jason.