Is there a way to visually display a unit's range?
In the original starcraft there was no way to tell short of memorizing.
In starcraft 2 blizzard added this for a couple of units
- Siege tanks in siege mode
- spine/spore crawlers while being placed
- point defense drones
- missle turrets
- photon cannons
While roaches are still a no go, you can use crawlers to break such a siege. Just remember they have the same range as photon cannons
No, but you could try to determine the range (perhaps with the editor) and memorize it.
Precise placement (unless it's used to wall/block) is not that important...