Adding cuffs to a project?

I have knitted a soaker (diaper cover) in anticapation of the new arrival. And want to make more. But the cuffs. They seem too small. How can I make them look like this ,the one at the top white one.
Is it the size needle you use?
The rolled cuffs. My understanding is 1 st for every row. So if I picked up 26 st around the leg I should knit 26 rows? Is that how you get the cuffs all pretty.
Thanks for any help!! The baby is due in 8 wks and I need to get to knitting!!

No you don’t have to knit that many rows, 5 or 6 should do it as long as they’re knit in stockinette. What `1 st for every row’ is the guide for picking up stitches.