This thread at wordpress.org – http://wordpress.org/support/topic/content-shown-based-on-user-role – suggests using the ‘current_user_can’ function
This thread – http://wordpress.org/support/topic/display-a-custom-image-only-if-user-role-is-contributor – suggests you can use it like ‘current_user_can(‘contributor’)’ for different roles.
I haven’t tried it but it sounds like it should work.