Restriction on non flat surface
 

Hello, I'm trying to place a movement restriction on ANSYS of a roller support for a structure, but it's not on a flat surface, but on an slopped one... Can anybody tell me how to work this out please?
Thanks!

ps: It's like the support on the right hand of the attached image, though my problem is with a 45 degree angle.
ps2: If it's still too hard to understand, send me an email and I'll send you a diagram of the problem. Thanks!

http://session.masteringengineering..../ME_MC_5.2.jpg