sixto.exe. Best rock remixing program in the world.
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Anyway, now for a real answer.
There is no one sequencer that's better for rock music; any half decent program will work for any genre you can dream up.
If you're looking for a sequencer, FLstudio, Sonar, and Cubase are all pretty popular.
If you're looking for something free, Reaper is excellent from what I hear. It's not technically free, but you can download a full demo with no built-in limitations, and it's pretty cheap to buy if you like it.
If you play guitar or bass and want to use live recordings in your music, you will need a decent audio interface. I believe there are some that will suit your purposes for well under $100. One you might try that's specifically designed for guitar is the line6 toneport.
If your audio interface doesn't have it's own amp-modelling software, you'll need a VST amp modeler. If you're willing to spend money on this, I HIGHLY reccomend Amplitube 2. If you want free options, I suggest you check out Sixto's guide.
If you do not play guitar or bass yourself, then you'll need the sounds for that. There are a number of free soundfonts at www.hammersound.net; you'll need a VST soundfont wrapper in order to use those. I use SFZ.
You can also find a number of VSTs for just about anything you can possibly imagine at www.kvraudio.com.
It's extremely difficult to get a fake guitar to sound real, and nearly impossible to do with only free stuff. Nevertheless, it's a good idea to experiment with free stuff before shelling out the cash for a commercial guitar library.
One thing to keep in mind is that there's a lot more to a guitar's sound than just the tone of the sample. To get a realistic sound, you'll need to humanize the part; add pitch bends, slides, and so on to make the performance sound less robotic. You can try running your sampled guitars (even the ones that already have some distortion) through a distortion and/or amp modeler VST.
There are probably other people who can be more helpful than I can in telling you how to fake guitars; I always use real ones, so I'm not really an expert on how best to use fake ones.