I did as much research on the Roadster as I could between 2008 and 2009. Tesla was very responsive to my questions and suggestions, sometimes saying that they were already looking into similar options. Here are the numbers I was given, and I hope they're not out of date since April of 2009:
5 bolt pattern, 110 mm' pcd
(this is in between the standards of 5x100 mm & 5x4.5" a.k.a. 5x114.3 mm)
M12 x 1.5 bolt
stock cast aluminum wheels: 10.2 kg each (total 90 lbs by my math)
optional forged aluminum wheels: 7.7 kg each (total 68 lbs by my math)
I run SSR Wheels on my older gasoline two-door, and I really like their SSF (semi-solid forged) Type-C model. With tires, they actually weigh less than the compact spare! But this is for the CRX Si.
Now that I finally have a Roadster 2.5, I am trying to find a way to get SSR Type-C SSF wheels in a 5/110 bolt pattern. They do not seem to have a 16x6 wheel, but they do have 16x7 and 17x7.5
$450 16x7.0J +42 offset 12.1 lb (normally 5/114.3)
$510 17x7.5J +49 offset 14.9 lb (normally 5/100)
A set of these for the Roadster would only be $1,920.00 and would total 54 lbs. That's a savings of 14 lbs versus the $2,900 forged Tesla wheels and a savings of 36 lbs versus the stock cast Tesla wheels.
As to the discussion about "performance," I suggest that the handling differences of low-profile tires are only sometimes useful, whereas reducing your unsprung weight will ALWAYS be useful, thanks to physics. Provided you don't somehow drop the weight too much - which should be impossible with that battery pack - I favor lighter wheels much more strongly than low-profile wheels. Note that larger diameters are always heavier than smaller diameters, at least when comparing the same technology. My theory is that extremely large diameter wheels are only for show, not for setting actual records.
If anyone has ordered SSR Type-C Wheels with custom Tesla Roadster bolt patterns, please contact me or leave a response here! I am just starting my research into whether these can be obtained, so any help would be appreciated.