Insulation, Radiant and Vapor Barriers - insulating a very small attic area but not sure how

I have a small room that juts off the back of the my Cape style house. There is no heat in this room but when the house was vinyl sided they insulated it then. There is also a crawl space under this room, and insulation under the floor has been put in. There is however no insulation in the ceiling of this room. We have turned this sun-room into a play room for my 18month old. With the winter coming I want make it warmer that it has been in the past. I need to know what i can get into this space. I can get into the crawl space and get to the edge of the sunroom but there is no way for me to fit batts of insulation in there. I could blow it in, but the area is only 6 x 10. Is there any other straight forward way to insulate this ceiling?

Hi True, there are other issues which make it difficult to give complete advice, like venting, and connection to the main attic. Those aside, some blown in insulation would help. Another way would be to glue and nail a couple of inches of rigid foam to the inside surface and cover with a layer so sheetrock. Maybe a little bigger project, but it is all done from the inside and it is a small room.
just some thoughts
Keep warm
Bud