Following a nerf every patch for the last four, the Roach is no longer a solid tanking unit. The roach is best used as a tanky dps now with an emphasis on changing mercs to a t3 after your early game advantage has wasted away. Beatles, the upgraded form of Roaches, are great as long as your enemy never buys an observer or radar tower, and doesn't notice the ripples in the ground that give them away. Their ranged attack is weaker than the roaches, so unless you're going to ambush with them CONSTANTLY, do not upgrade your roaches, and rather change mercs instead.