1. burrow (commonly used vs the 6-7 gates all in)
2. infestors

if the protoss mix in immortals, any sort of roach defense will die. immortal range + sentry FF imba. -DRG

from what u told me, it sound like a 6-7 gate +1 allin timing off 2 base...
with that, there is no observers...
the allin works well by using FF to isolate and pick off the units of the zergs little by little...
using burrow, u can run away or move towards the army and thus dealing loads of damage to his army...
the moment u defended the push or kill a significant amount of sentry, u should win the game since the protoss spent too much gas on sentries and is really late on tech...

against a toss that dont FFE and when you go up ramp theres less than 3 sentry, just saturate your 2 base until about 6-6.30 minute throw down evo then spore crawler and mass ling and you are fine.

what can 1 base toss do.

dt (spore)
stargate (spore) this 2 strat will show less than 3 sentries. on top of ramp

4 gate, 4 gate warp prisms, immortal all in (these all ins require alot of unit, if you saturate 2 base, +1 carapace lings can just out produce your opponent but you should engage at favorable spots and try to snipe proxy pylons.)

if they on top ramp but you see alot sentry means its a sentry expand. always count sentry and if his 1st 2 unit is zealot stalker, more than likely he is gearing for some 1 base play.

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Added on February 17, 2012, 6:47 amthats why everyone FFE unless the map is retarded. more options later on.