As we've been told previously -- and it's been a while back, but I haven't heard about any changes -- the Roadster will come with a Blaupunkt stereo receiver. Blaupunkt also supplies receivers for the Lotus Elise. These are infamous for their poor audio quality, and Lotus owners often refer to them as "Blaujunk".
From what I've read over on the Lotus forums, most owners either don't care about sound quality (the high-revving 4-cyl engine is what they want to hear), or they replace the Blaupunkt head unit pretty quickly. Replacing all the factory speakers is also a likely move. Tesla at least are offering a premium speaker option.
A recent photo of the EP2's interior showed what appears to be a Blaupunkt "Key West" MP36 receiver, which is the lowest priced CD unit that Blaupunkt offers. A survey of owner reviews at the Crutchfield website turned up complaints that these units overheat and then "eat" CDs, FM radio reception is poor, and the iPod interface is plagued with electronic noise.
Also noted. . . Blaupunkt does not offer any receiver units that play back AAC-encoded music from CDR discs. Sony, Pioneer, Alpine, Kenwood, Panasonic, Clarion and JVC offer receivers with this feature. Since Apple are now selling non-DRM-protected music through the iTunes Music Store in AAC format, this could be a useful ability.
Now keep in mind that most car companies have a long tradition of putting in laughably bad stereo receivers at the factory. I'd hoped Tesla would go a different route, but. . . it doesn't look that way.