This describes a build that puts on early pressure with 7 roaches at 5 minutes.

Rough build that could probably be refined a bit to sneak out some more drones
or shave off a few seconds on the roach timing.

If you have the timing of a god you should be able to have your roaches all pop
at about 4:50. In my quick tests I've managed a best time of 5:02.

Build:
9 overlord
14 pool
15 gas (pool about 50% complete)
15 overlord
16 queen (as soon as pool finishes)
18 overlord
19 roach warren (queen about 2/3's done)
- vomit larvae when queen pops
- stop making drones and pool larvae
- make 7 roaches as soon as larvae pop off
- transfer drones from gas back to minerals
33 hatch
32 overlord
- drone like crazy

Fed build into sc2calc:
http://bit.ly/f9omhC

Notes/Refinements:

- Had a bit of extra gas when I made the roaches so the extractor could have
  been put down a bit later
- There was a few second gap between when the roach warren finished and when
  the larvae vomit was done. So the roach warren could have been put down a
  few seconds later.
- It may be possible to squeeze out another drone before making the roaches
  so you would be at 34/34 as soon as you make the roaches. Need to test the
  timing of larvae creation to make sure making the drone wouldn't prevent
  making 7 roaches right when the larvae vomit finishes.
- Expanding at around 5 minutes is a bit late. Want to compare drone production
  and expand timing with a safe 6 speedling + expand build at 5 minutes to see 
  how much your economy is impacted by the build.
- Did the same build with a single extractor trick and ended up with roaches
  at exactly the same time only with more chances to mess up.
- Could try a double extractor trick but don't think it would make much of a
  difference.
- Need to check the exact timing of placing the warren and compare it to when
  a standard 2 rax build would place the second rax to see if it is possible
  to scout that build before going for this.
- Based on some replays of people doing early roach builds it should be possible
  to shave several seconds off the build.
- Seems to impact drone output by about -2 vs a 6 speedling opening.
- Delays expansion by about 1 game minute.

Mechanics of the build tested against easy AI:
http://pub.easytospell.net/7roach.sc2replay