When I fisrt had this setup in a rented flat, I used these expandable poles from Migros. They go from floor to ceiling and can be adjusted to your ceiling height, fine adjustment is via the threaded foot and has a sping inside to enble it to be 'jammed' in place.

I then stapled the screen cloth to a length of wood and hung this on the poles.

the same idea could be used to hand from curtain rods and/or adapt a pull-down or motorised screen.

Mind you I'm not sure how good an idea it is to mount a screen in front of a window. Unless you add some 'black-out' cloth behind it (mind you the cloth is probably thick enough to stop light coming through unless you have a 'back-projection' cloth :-).