I think your insulation is fine as is! You might want to consider a Radiant Floor Heating system. This would be installed from the garage side and insulated with a sprayfoam. (I'm not sure if batt insulation is added or not but it may be since your bedroom floor is 'in the garage'.)
In any event, do the BEST job you can to prevent air from entering in the bedroom from the garage (even if the garage is heated.) Also, give your floor an EXTRA go-over to prevent cold air from being drawn UP and INTO the bedroom. (Minimal expansion foams are available, among other things.) If you go with a Radiant Heating System, you won't need to heat the bedroom so this may save you $$$. Consider a separate 'heating zone' for the bedroom.
If there isn't a 'room' above your BEDROOM, be sure you have soffit and ridge venting along with Soffit Chutes to 'cool' the roof. This is critical if your ceiling/roof in the bedrooms is cathedral. If you don't vent properly, the roof will age right quickly, and your bedroom will be a pressure cooker in the summer!
Oh, and be sure to get CO2 / Fire Alarm for the bedroom! Others will add more info. For now, my best to ya and hope this helps.