cold rooms

In our house the bedrooms get so cold at night. The boy's room is the worst, I put a thermometer in there and it was 61º in the morning. The other two bedrooms aren't much warmer. All of us wake up freezing, even with the doors open to help the heat move. The thermostat is in the living room, no matter how high we set it the bedrooms are still cold. We've been setting it to 75º at night but we've tried it as high as 80º, in the morning we run the a/c for a little while to cool the main part of the house back down. The bedrooms warm up during the day from the sun beating down on the dark roof. I called the maintenance people to see if they had any suggestions and they said it's a common complaint of people in this floor plan and there isn't really anything they can do about it. We had the opposite problem in the summer, the bedrooms were hot while the rest of the house was cooled by the air conditioner. 

I've been thinking of putting space heaters in the bedrooms but I'm really nervous about it, same with fans at the doors to blow the warm air in the hallways into the rooms. Is there anything else to do?

Where do you get safe space heaters? Is there a particular brand to look for?

 

 

I'm not sure what the heat is called but there is an electronic thermostat in the living room, a gas furnace in the garage, and each room/hallway/walk in closet/bathroom has 1-2 vents in the ceiling that blow hot air in the winter and cold air in the summer. 

ETA:  It makes a huge difference to have the heat underneath you( rather than above you with an electric blanket).  I've slept on one year round for years.  It helps me with my muscles.