I used McCalls M7229. It's a pattern for costumes for a nativity play. I bought it for the large robe because of the angel wing sleeves. I made the front open and added some width all around. But the sleeves were too tight in the armholes and I ended up remaking them. The flare at the wrist was good. Nice pointy wizard sleeves. For the small one, I used the sleeves from the large pattern (cut down of course) and modified like the large robe. Basically, I just drew a straight line from about the elbow up to a point several inches below the armpit. The robe itself has pretty straight lines for the armhole as well.
I had to makeup the hood...took a few tries with an old bed sheet.
The body of the smaller robe was an old A-line girls dress pattern I had. Probably doesn't exist anymore, it's over 30 years old! Any A-line nightgown or dress would work.
But search the web, there are some decent robe tutorials, sort of DIY but they get the point across. I probably would have spent less time if I had just made my own pattern.