Insulate concrete flat roof

[chriz1]

What's are my options to insulate a concrete flat roof?  In This area of the house its noticeably colder and when I replaced the tiles on the small roof at front of house discovered below is a flat roof with no attic space for insulation. 

 

I was thinking internal insulated plasterboard or can I lay insulation boards on top of the outside of roof but I'd imagine the huge mass of concrete would still make the inside area of home cold and need to be all heated up before noticing a difference Inside? 

See pics 

[Marvin]

Well you can insulate on top and this would mean the concrete would slowly warm up to the internal space, however it maybe difficult to avoid cold spots at joins  with external walls which could cause damp surfaces. 

May be better as you say to insulate inside.

 

However, more clever people will know others remedies I'm sure. 

 

Best of luck

 

M