You need existing blinds.
About two yards of fabric.
And some sort of glue.
I used a glue gun.
Very simply, you cut out all of the blinds except for the "bones" of your roman shade. I left 6 blinds. . . they were about twelve inches apart.
Then cut your fabric so that it overlaps the stretched out blinds about two inches all the way around.
I ironed my fabric so it would have nice creases where I wanted to fold it.
Then I laid everything out on the dining room table and started gluing. I did the "bones" and edges first, then the bottom, and glued the top at the very last when it was actually hanging on the window. **Note: beware of gluing the cords. You want those to move freely.
The detailed directions on Apartment Therapy's site absolutely forbid hot glue. Call me a rebel, but hot glue works just fine. But maybe that's because I use my grandpa's super duper industrial florist's glue gun which is a step above most cheapie versions.
The hardest part is carefully cutting a hole for the blind cords. I cut a tiny, tiny slit.
This took me about an hour. . . it is seriously one of the easiest projects I have ever done. My total cost was $15 and that was because I bought heavy canvas fabric just because I liked the pattern on it. $2-$3 per yard cotton should work just as well.
Detailed directions at The Little Green Notebook. Or google "roman shades out of mini blinds" and see what you find.
Jacob's room is next, but I'm looking for some atlas / world map fabric first.