1 base lings/roach is also very strong. Even a 4 gate won't counter it due to the nerf on warp.
Zerg is a broken race. Sorry for QQ-ing.
Dennistoo you should be easily defeating 1 base ling-roach with a 4 gate. What you are likely losing to are 12 drone roach speedling all-ins. If this is the case your problem is failing to identify this with your scouting and just assuming that a 25 probe 4 gate should beat 1 base zerg. In actual fact you are at DOUBLE his workers, and so holding should be INCREDIBLY HARD.
Basically Sheth says if you have X number of workers over your opponent at a certain time and they execute an attack properly, they should win. This rule applies for all races and so you need to learn to identify what your opponent is doing. If you scout a 12-14 pool and similarly timed gas you need to constantly check for a hatch going up, and seeing if the roach warren goes up as soon as the pool finishes. If a hatch goes up then your 4 gate should easily get up in time, if they get a roach warren immediately after a 12 pool finishes then you need a 2nd gateway and to start chronoing sentries, you also want to consider walling yourself in with a pylon as you probably already have +50% workers over your opponent and need to be extra safe to let your added income kick in.
As for head-on, no super early rush, 4gate vs 1 base ling roach. There are some simple things to take note of:
Roaches > zealots (can kite all day)
Zealots > zerglings (as long as the lings cant seperate and surround lone zealots)
Zerglins > stalkers (the stalkers do very little damage to lings)
Stalkers > roaches (bonus damage, added range, as long as you are off creep can kite and micro vs them easily)
Sentry > Zerg.
So if you are facing roach ling with pure zealot stalker then 1 way to lose would be to let the lings surround your stalkers whilst the roaches kite your zealots. If you control so the zealots guard from the lings and the stalkers focus the roaches then it should be a close fight.
Now add FF to the equasion, especially vs non-speed roaches off creep they suddenly become very bad, lings often cant get surface area and essentially the toss 4 gate army gets infinitely stronger.
So to beat 1 base ling-roach with a 4 gate you want to keep a hidden scouting probe to verify that they aren't expanding. Once you know this you can let your sentry count build up to say 5, so they can bank energy, and then swap into heavy stalker zealot. You still don't want to get caught outside your base and surrounded before you have a decent unit count up, so you want to be conservative for a while before moving out, then one you have a large enough army the banked FF should allow you to dominate your zerg opponent.
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