Even the DVD-ROM is optional, since drive-to-drive copy is rarely a good idea.
I don't know if this is true or not anymore, but I remember reading somewhere that, if you can afford it, it's a good idea to get a CD-ROM/DVD-ROM drive in addition to your CD-RW/DVD-RW drive.
Basically, the article I read contended that, because of the write mechanisms on the rewritable drive add more weight to the drive. What the author said was that the extra weight increases the wear and tear on the drive, thus causing it to fail earlier. If you did a lot of reading of DVDs and CD-ROMs, it is this reason that the guy said you should have a regular DVD or CD drive in addition to your burner.
...But like I said, I don't know if that's true anymore. I will agree, though, that drive-to-drive copying isn't a very good thing to do, considering data throughput issues.