Nice tip - I didn’t even know there was an erase mode in the foliage tool!
The only trouble with it is that if I re-simulate the forest (say, to add a new tree or rock type), then all the carefully erased trees over my road pop back into existence again - grr!
Maybe the best option I have is to add a whole truckload of foliage blocking volumes to the entire length of my roads. It’s labor intensive, but on the other hand it saves having to manually re-erase the trees on the roads when messing with the forest.
It would be spiffy if they added an auto-foliage-blocker option for landscape splines. The engine knows where they are when it spawns the foliage anyway, so I figure it could do that entirely procedurally.