I still think its likely a Trademark issue, there are two posibilities that I see, First Saleen is technicaly a manufactuers, and Roush is a customizer. Meaning Saleen buys cars from Ford under a special agreement, then sells them as if they made them. Therefore laws that insure the supply of aftermarket generic body parts may apply. Second Roush wheels spell out the name "Roush" which is easy to trademark, Saleens appear to use a stylized "S", this is much harder to trademark, as even slightly different typestyles may be enough different to slip by the legal system.
Ike
p.s. It may also be that the Saleen logo is on the center cap, which is often not included with the aftermarket wheel. (you get the Saleen style wheel, but if you want the "S" you have to buy it seperately), where the Roush wheels have the name printed on the spoke