Tesla did work with Lotus on the car but the Roadster only shares 7% of the parts with the Elise. Every body panel on the Roadster is unique; the only exterior part in common is the rear view mirrors. The rear view mirrors are critical because you have very limited rear window visibility when turning your head.
Amended 3/26: Ironically the first stranger to stop me and talk to me about my car said “I like your Lotus and I like the color”. I clarified that it was a Tesla.