If the sunroof is stuck, the fuse may have blown, so check this first. If the roof rails/runners were dry or tight and as such, a subsequent strain on the motor, the fuse may have blown. Go to the cars 'manual' and look at the fuse diagram then find it in the fuse box. If the fuse is intact the motor may be "dead".
Whilst viewing the 'manual', check the section about 'faults' or 'roof window'. There is often access to the mechanism above the interior mirror on the roof lining, via a plastic panel. If a panel exists, you should be able to gently pull the panel off. There you should find a "KEY" which manually inserts into the mechanism in the same location and will allow the closure of the window.
Whilst I am not an expert, I did have a Renault Laguna and had to use this measure to close my sunroof a few years back, so hopefully it may work for you....
Davy Mac
June 2009