Well, most of it.* You should be able to rotate the actual terrain of most maps easily enough by just rotating the heightmap. Then you can bake the materials.
That just wouldn’t cover the materials (manually painted), objects, nodes, spawns, resources, foliage, etc.
Unless the map was entirely made in the Devkit (like Germany), as opposed to being converted (like Russia or Destruction) or being entirely made in the Editor and being unconverted. In which case, I believe the game makes a compressed file for each individual tiles’ heightmaps, so you wouldn’t be able to effectively rotate them.