It depends on the set-up I have put up. If they we're just hit on the ground by a Nair, Side-B, Forward Smash, I've noticed people have a nasty habit of rolling towards me after getting knocked down. I usually position myself to Up-Smash where their incoming tech roll will put them. Its a hard read, but it kills and it's hard to punish if they decided to roll in the opposite direction.
If they weren't knocked down, then I usually Side-B if they roll towards me or try to roll behind me. I tend to find people roll towards you when they are stuck at the ledge (I have this habit too). I would avoid using side-B to punish people rolling away as for me at least, It's way too slow, covers a small distance, and highly punishable. However, doing a side-B off the ledge is safe if you miss, but you do give up stage control- but Peach does have better ledge options than most characters especially with her having float. Down Smash is also really good at the ledge if they try to roll past you.
As for people rolling away, it really depends on the character I'm against. If they wanna roll away, let them. Free turnip pull for me. Otherwise I just chase them and wait for them to do a panic move or dash attack them if they try to roll again. It's more common I thing for people to roll again if their character has a short roll.
And for an extra chance, I sometimes use D-air if they roll towards me. It leads into a free Fair at low/mid percents and is fairly easy to connect on bigger characters.