Much, much more. Industrial-scale agriculture is by far one of the most devastating things that humans do to the environment; my focus on roads wasn't meant to imply otherwise.
(The larger observation is that, while we use more land for agriculture than we need, there is at least a prima facie argument that industrial agriculture feeds our planet. Whereas a 6 lane highway through a drained wetland to a low-density suburb does very little for our planet.)
Not all agriculture even feeds the planet. E.g. cotton grown in the central valley of california makes its way to mexico to become budget metal spring mattresses. Does the world need more metal/wood/cotton boxes that end up on the side of the road at some point in their lifetime? State economic planners seem to think so at least.
(The larger observation is that, while we use more land for agriculture than we need, there is at least a prima facie argument that industrial agriculture feeds our planet. Whereas a 6 lane highway through a drained wetland to a low-density suburb does very little for our planet.)