It is best to ask your local council or pop into a local surveyor and pay a few bob for reliable advise about this. You will have to have some plan for it and how you want it to look I suppose.
If its a simple conversion (and your roof can support it - that is what the council will be mostly interested in) it is most likely there would not be any problem with planning permission (and might not need any)
simple roof terrace with best chance
But like I commented your region, suburb might have estical constraints and dis-allow any external changes, eg solar panels, window colours, etc ,etc.
A design obscuring might be problematic.