The Roketa and Alpine use the Zongshen motor, while the Lifan uses...the Lifan (go figure!
) In fact, the Roketa might even be one of the several brands (I heard something like 9 in the US)that are manufactured by Zongshen and sold under a brand name. That might be the reason that Zongshen hasn't really made a big push in the US--their bikes are already here in force (i.e. Roketas are very popular)
I doubt the Roketas hit 65 stock--most brands come with 56 t rear sprockets limiting them to about 50 maximum. One of the few brands that come stock for real top speed is the LIfan with their 46/17 teeth combo. Stock, they hit 65 to 70 (mph, that is)