Roads are free decorative tiles that block the placement of buildings and decorations, but can be useful for organizing your characters.
Place or destroy roads using the button in the top left of the map editor screen. Open the map editor by tapping and holding on any building or decoration.
Characters, including NPCs like pirates and bulls, will walk along roads when they're not doing anything that requires them to be in a specific location. If there are no roads on the map, characters will walk along the edges of the map.
If you're having trouble keeping tabs on all your characters, try destroying all of your roads except for a small patch. That way, all of your characters that aren't doing anything will flock to one place and placidly walk in a circle like the filthy sheep they are. This makes it a lot easier to silently judge them, as a group and down to a single soul. They know what they've done.