I just looked at some pictures and descriptions of the roadster and it shows that transmission is all the way in front while engine is in the back. its maybe naive to ask 'why' but i will ask cause it bugs me much
Umm...... Neither the Roadster or the Model S has a transmission in it at all. The motor is bolted right to the axel. Well ok, there's a reduction gear between the motor and axel, but not transmission at all.
What picture were you looking at?