I think by default this mod uses landfill as the road tile. Would it be possible to set a customisable road tile? Say we placed the road material into the hardware store? It would use that material until it ran out and then revert to landfill? Backfilling the landfill when the material became available again? Blacklist stone brick by default I guess? For example, if I place asphalt road tiles into the hardware store, it would be awesome if it went ahead paving the world with that. Or I could put in a dektorio tile for a pretty village.

Heya, at this time it's not customizable, unless you unpack the mod and edit into the source code (constants.lua if you're interested). I don't think this feature will be on the roadmap soon.

Does that mean that when this mod is active, roads fully replace landfill? Does that mean there is no landfill in the game or do I pave over water with asphalt now?

Thanks. I've had a look through the source now. I see why it isn't customisable :D

So I guess where the roads are built, if it is consuming the road building materials, it would need to also do this sort of check first:

local cost = Consumption.consumeRequired(construction_materials, hardwareStores, city)

Default to landfill if the material is absent to prevent the city growth stalling, and rely upon the tile queue to back-fill? This is sort of a separate issue to customising road surfaces. Anyway, I think this is straying away from mod discussion into developer discussion.

I think that's something reasonable to do! Will consider it for a future update, but if you're interested you could contribute the changes, too.