Actually, Towers need a buff
Subjectively I can only say that the Rook should not be nerfed at all.
I very rarely encountered really dangerous Rooks and altough his tower farms are annoying, they are not too strong imho. Remember: It takes a lot of (dangerous) time and mana to set up a secure tower farm.
One thing I would like to see is that the towers should die if the Rook dies. Same as minions.
But that would be a nerf....
Towers actually need a buff. First of all, less restriction on placement. Seeing "aborted" when I try to place a tower at my feet or near a corner/edge/tower is really annoying. Second, power of the tower 4 (the one at level 10) lets you have more towers and costs less mana, but you have to get mana regen items to have a decent tower farm back when they used to cost 400 mana, and the cooldown is too dang long to put down 8 towers for how relatively ineffective they are at that point in the game. Either cut the cooldown in half, put the mana cost back at 400 and make it spawn 2 towers at once, or simply make the towers do a LOT more damage (OR HAVE SPLASH PLEASE). The 3rd feature they need is for the chain effect thing to actually work to provide extra damage. Putting towers near each other is the only way to make decent damage, but it gets owned by aoe and takes way longer than minions of minion builds to replace (and minions have an advantage of mobility, so they can run away from being owned anyways).