I recently came across this product:, which is a stainless steel shield to place between your mountain cleats and your carbon soled shoes, to prevent damage to the carbon.
Has anyone seen something similar for a road shoe?
You could use a pair of these stickers.
As far as I know most road cleats are plastic cleats and are not going to do significant damage to the shoe (being plastic and large rather than metal and small) so no protection is needed.
(There are some road cleats which are metal, as described in comments.)