My RM has always been indifferent to the cold, though it likes to foul plugs a bit more when it gets below 40 degrees or so.
Two old school tricks I have seen work are;
Gas on, choke on, remove gas cap and using your mouth, pressurize the tank with your breath and hold for a few seconds to ensure the carb bowl is full. Try to start it.
Gas on, choke on, lay the bike on its side until gas come out of the overflow hose, effectively flooding the engine, then kick as normal.
The main reason most cold starts are a b*tch is there isn't enough fuel in the chamber.