Here's another thought.

Like Hamish said, if you think the sweater needs to be "fixed" at the bottom, it is perhaps too long. But, even if it is an OK length, it may be too "big". I have several sweaters that were just too big around for me. I'm 6'3", and if a sweater is not "long" sized, I have to buy an extra-large to get the sleeve length I need. That means that it was made to fit around someone with considerably more girth than I have. Thus the sweater hangs badly, in my opinion.

My fix is to take up the slack along the side seams. Most sweaters are joined along a seam from the arm pit to the hem. Turn the sweater inside out and stitch (small and numerous by hand...use a machine if you can) another seam inside the first. I'll take up several inches at the hem end, tapering to nothing at the arm pit. When done, just cut off the excess material (which includes the original seam) and you're done. By fitting a bit more snugly at the waist, you solve the need to tuck or roll or otherwise adjust the bottom of the sweater.