Unfortunately we do not have a product we can recommend to paint the internal face of a polycarbonate roof. 

If you were to want to paint the external face of the polycarbonat, it is clean, dry, sound and prepared as detailed in the technical data sheet you could consider Britannia Aquashield Eco.

This is available in black, grey, or solar reflective white. 

Please note that brush marks would be visible on the inside.