Greenhouses, Sheds and Sun Rooms - sunroom conversion

We have a sunroom enclosed on three sides with what used to be the exterior of the house. the roof is flat with a large skylight in the center. the exposed wall is essentially windows and a glass door. It does get cold in winter and too hot for use in the summer. It is build on a cement slab, and we would like to turn it into a greenhouse to grow year round. there is already a ceiling fan to help with cooling, but what so we need to do for insulation? there is a knee wall about 2 1/2 to 3 feet tall. I don't know how well it is insulated as the inside is painted plywood and the outside sided to match the house. The previous owners used it as a warm weather living space and had their hot tub in the space. It has indoor outdoor carpeting, but that is easily remedied. My question is this. The roof, being flat is in need of resurfacing. Will I have enough light with the wall of windows and the skylight, or should I forgo resurfacing and look into some other kind of roof situation?
Thanks,
Nicole

Flat roofs are notorious leakers/rotters, skylights do not boast clean records either.

I would seriously consider rebuilding the roof with pitch if possible. The plants require light from above (or they grow funny) so a bank of skylights is the minimum to call this a "greenhouse".

Better, I think, tear it all off and kit together a real greenhouse.