Mini blinds (the cheapest ones you can find to fit your window)
Fabric (yardage depends on the size of your window) - I'd recommend an irregular pattern in case you don't like to use a level like me. If you're using stripes there won't be much room for error.
Measure your window and determine how many folds you need. I don't think there is a right or wrong answer here. I went with 6.
Lay your blinds on the floor fully extended. Carefully cut away all of the thin, ladder-like strings. Do not cut the lift cord (the thicker cord).
Remove the plastic plugs from the bottom of the blinds and set the bottom slat for later. Remove all of the slats leaving only enough slats for your folds (I kept 6 slats for my 6 folds).
Reinstall the bottom slat so that the length of your window and the fully extended shade are about the same size (it doesn't have to be perfect).
Cut your fabric a few inches larger than your fully extended shades on all sides.
At the top of the mini blinds fold the top edge of the fabric over and iron a crease to make a crisp edge. Then glue that to the top rail leaving the ends open so that you can slip the rail into the brackets during installation.
Place your slats at even increments where your folds will be. Fold over and iron a crease into the sides of the fabric. Glue the slats to the inside of creased fabric folds.
Wrap the bottom like a present and glue.
Let your assistant take a snooze while you wait an hour or so for the blinds to dry.
Install using the standard mini blind instructions.
Voila! Roman shades for a few bucks! In hindsight I would have splurged for thicker fabric but that's the beauty of DIY on a budget...you aren't married to it and can change it on a whim!