ynphea

I don't think wrobot has a way to get it from memory, so you will probably have to get it from lua.
Edit:
https://wowwiki-archive.fandom.com/wiki/API_UnitGroupRolesAssigned
 
string SomeString = Lua.LuaDoString<string>("return UnitGroupRolesAssigned(Unit)"); Where you replace the "Unit" with whatever. (Player, Party1, Raid1, Target etc.)

Edit Edit:
You can iterate over your party members with a for or foreach loop. ?

It depends very much on what expansion you are working on. WOTLK has a definition for a tank, whereas tbc/vanilla doesn't. (In this case you will have to define the tank yourself.
You can use the "help party members" option in advanced settings to make sure that the party begins combat with whatever anyone else in the party is attacking.
So in short, with this option on: If your tank attacks a target, your bot will automatically help the tank.
Target selection is something completely different, which if you don't override it will choose by itself.
In order to change the target manually, you have to "stop" your current combat and restart it with a new target. It's actually not as easy as it sounds. ?