Make more roaches and infestors than the other guy :]. I make hydras in this match-up too, which can really change the tide of a battle. Alternately, you can try to hit the vulnerable timings of your opponent (when he is saving for infestors, upgrading them, etc). Just power out roaches since theoretically they can't hold pushes, while building the infestor pit and pathogen glanding and then building 4-5 infestors.

But yeah, hydras are good to mix in if you want to go for the long haul.

A strategy my friend explained to me that I've been having a lot of success with is doing an upgraded roach timing attack before infestors get out. I've been upgrading just +1 attack and start massing roaches as the upgrade begins. I rally all of the roaches to somewhere odd--like a bit away from the base so they're not easy to scout. Then just push with all your roaches once the upgrade is almost done and time it so it finishes right as you crash their gate.

The key is to attack before infestors come out, so you need to be quick about it.

I expand and drop my infestation put and 2nd evo as I push out with the roaches. It's aggressive--you need to do damage in order to keep up if they've been building their economy correctly, but it's pretty strong. I've been having good results with it.

Its a tough match up, you need to have very good scouting, you want to have an overlord close enough to their mineral lines to get a drone count try and stay 1 drone or so ahead in the early game, and in the mid game 6-10 drones ahead, you can do this by constantly scouting with speedlings and overlords while hitting all of your injects and being careful with the spending of your larva. I like to do heavy spine defense on maps I can take early thirds like shattered or Tal Darim, still with infestors although muta can be a good option, this lets you save some larva for more drones while still being pretty safe to most attacks.

The ultimate composition IMO is broodlord hydra infestor with some roaches, if they have broods just a few corruptors work magic like 3 or 4.