Upgrades are key. If you scout that he's going roaches, you need to build your own roach warren and two evo chambers immediately. When I open against zerg I usually pull off gas after I get 150 gas (Enough for a bane nest) and start speed and get a bane nest going and refill gas with new drones right before speed finishes meanwhile I am just being aggressive with my lings. There are three builds I normally see, mass lings (Good, I will crush them with banelings), roaches or turtle zerg to muta. If I see roaches, I start my own roach warren and two evo chambers to get +1+1 and a lair. Those initial lings I made are now going to be posted outside their base, never engaging the roaches directly unless I can pick one off safely. Lings are terrible against roaches. This way they are forced to be defensive with them while you are getting your +1+1 and massing a roach army. 1v1 1 roach will kill 1 roach in 10 hits, but if it has +1 it'll kill it in 9 hits. It takes 10 roaches to kill 1 roach in one shot, but if +1 is done it takes 9 roaches. If +1 armor is done then i takes 11 roaches with no upgrades to kill it. Another thing I like to do is get +2+2 immediately when lair is done and get 2-4 overseers and use their contaminate on their evo chambers so you have an advantage for much longer. Another option thats sure to confuse them is it takes 9 banelings (8 with +1 malee) to kill a roach so if you get 20-30 banelings you'd clean up their army but its really not that efficient. Burrow is also good to have for banes/roaches in general if you have the gas.