Yes all site components will slope with the topo. you pick the element and a pick host button will appear, once you click that you then pick the topo surf. see my reply to the other question on curbs for a file with many curb families.
If you don't mind me entering this, i'm in a similar situation here with getting the curb i've drawn to follow the road which slopes along my topography. could you explain that host? And possibly attach or head me to the curb file you mentioned.