Civil 3D has so many colabrative tools, this one is a hidden function that is very useful and easy to use.
To assure the slope meets existing ground use the nearest osnap when selecting the surface. The modified slope should now be inside the ROW for this section.
Each section is modified individually and updates are shown in planview as well.
Edits are quick and efficient, but not suitable for all designs. If this is a consistent issue, look at different subassembly for desirable results. I would recommend DaylightInsideROW to start.