Miles' romper was a bit more complicated. I used a raglan sleeve romper he already had to create a pattern. I used the same tutorial for the sleeves, but left one seem partially unfinished so I could add some snaps.
For the crotch snaps, I created a facing for the part around the legs, sewed it on right side to right side and then turned it under. I turned the raw edge under and sewed along the folded seem. This finished the edge and gave some stability for the snaps so they wouldn't rip through the fabric. It turned out pretty well and wasn't too hard to sew.