Here's an easy pattern for a rolled brim hat that I use all the time.
Use a multiple of 9 stitches on #8 circular needles. 54 for a childs hat and 63/72 for an adults. It is straight knit until you reach 6-7 inches and then you start to decrease. Knit 7 and then 2 together. knit the next row. Continue decreasing with one less stitch between until you have only 8-10 stitches on the needles. draw the yarn through and secure. This enables you to have a nice hat with no seam to sew. I've made lot's of these in a variety of sizes. If you want the hat to be longer just knit to 8or 9 inches before starting the decrease. Happy knitting! Becky