You could make custom Roman shades with metal arches made to fit the windows. If you are a handy sewer and know someone who can do the metal, it's quite doable. Getting a pro to do the whole thing might be tough. You could do a Roman shade from the ceiling. If the material was a thin, billowy material, you could run it along the entire width of your windows at the top of the wall.

If you just need some shade, like only at the top of the window, you could make a valance.

I like the idea of custom made Roman blinds. Another option is cafe curtains.

Bottom up Blinds

I know you said you don't want curtains, but I think the best solution would be to put stationary drapery panels on either side of all the windows for a more finished look. If this is an office, you won't need much privacy. Leave the windows themselves uncovered.

Examples:

Parade of Homes 2012 · More Info

Draperies and Window Treatments · More Info

If direct sunlight is the issue there's always solar window film.

The most cost-effective approach would be to install an outside-mounted roller blind with reverse roll, without needing to consider arch issues.

I've never thought of a reverse roll but it makes sense.