I'd like to install a door 'kind of' on this room... help please!

Is the height from floor to ceiling enough to install a door? You would need to frame out a wall with an opening for the door.....https://www.google.com/search?q=framing+wall+with+door&biw=1016&bih=642&tbm=isch&tbo=u&source=univ&sa=X&ved=0ahUKEwjj44Tnp7PSAhVG5yYKHZRhBgwQsAQIIA

Would you wan to put drapes up?

You may end up with a short door. Average door height is 6' 8" with at least 2. 75 " for a header.

How about a bifold door?- The louvred kind would allow air flow in the attic and are available in a number of different widths. The narrower ones would probably fit in your restricted headroom space.

you could add saloon doors (double full height thin doors on springs). that way you could open them either way and you wouldn't need as much space inside and would always be out of the way.

You might want to consider dual barn door sliders on a rail that meet in the middle!!

The slider takes the "range of swing" out of the picture giving you more room. It also eliminates the door hitting the ceiling when swung all the way open unless you have some type of stop. You could do just about use anything that fits the décor. I think there is exposed mounts and concealed. if you go with exposed it fits more of the rustic barn door type. Look on Pinterest.com to get some ideas.

Buy a solid wood door and frame and just cut it down to the size you will need, using the peak as a center point and measure out 15" on each side of the 30" door. Sliders and such will need room to open, so the slant of the roof will tell you how tall they can be. If you do cut something down to fit, be sure and tape where you are cutting to help keep the wood from splintering at the cut. If you can get your hands on some cardboard from a frig or something play with that to tell you just how big the door can be.