Hey guys. I'm mulling over doing a rock module. I was wondering what types of synth sounds are used in rock. Synth bass, keyboard, strings, some sorts of leads? Any ideas.

For inspiration, listen to Nori Ubukata's add-on patches for Synthmaster, especially "Art Rock Basics".
 
The synthesizer has been an integral part of rock music since the introduction of the Minimoog first made it affordable.
 

 
If had to rate the relative importance of categories based on usage over the past 40 years it'd be 1) monophonic leads, 2) sweeps, 3) basses, 4) pads. The first three have been most-used because early synths were monophonic, which lends itself best to those types of sounds. 
 

Nori Ubukata's patches are a great suggestion if you have SynthMaster.

I think there are a bunch of useful rock synth sounds in Native Instruments Monark (spelling?).

Thanks for the ideas guys.  I don't have synthmaster but I can probably find some reviews / demos.

Synthmaster is what I would suggest also. AFAIK it is the only one that has a prog rock sound set. I believe it also has some 80s sound sets too. Luckily Synthmaster is often on sale and not only is it one of the most powerful synths. It is also one of the cheapest.

It sounds like he is wondering what sounds to put in a future sample set more than looking for a synth to get.

Moog will figure prominently (even the Beatles used it on Abbey Road) as will Mellotron.

Beyond classic prog, don't forget a lot of late 70s stuff like Styx "Come Sail Away", The Cars, Billy Squire "In the Dark", Foreigner 4. Led Zeppelin's "In Through the Out Door" is a great example as well, particularly the strings on "I'm Gonna Crawl".

Asia's first album and Yes's 90125 also have some pretty good synth sounds.

I don't know if you want to include new wave sounds in your collection but you could probably make a pretty good size pack of sounds from The Fixx alone.