So how is the electric Roadster heated for Canadian winter driving.
There is A/C that circulates battery cooler so you get benefit form it, electric heater (IIRC) and seats are heated.
For best efficiency seat heaters are the best.
How cold weather are you talking about? Canada is a bit large place, so one temperature scale doesn't apply every place. AFAIK Roadster battery needs to be plugged in in temperatures below -20C if it is not used. That keeps batteries (and coolant) from freezing.
A usual winter in Southern Ontario can reach as cold as -20C / -30C.
If you live out in the Prairie Provinces, you toss out the conventional numerical measurement and use verbiage...
...pleasant (-10C) / cold (-20C) / very cold (-30C) / damm cold (-40C) / Holy $#!% (-50C) ;-)
Bottom line is that in most of Canada, you'd better plug that puppy in.
The battery is heated using battery power. So leaving it unplugged at -20 for a few hours will just reduce your range a little. But leaving it like that for a week is a really BAD idea.