Use a condom.
But, in all seriousness, one thing I love against people who roll: run towards him and dash cancel (crouch while running) in front of him and flick back on the c-stick if he rolls.
You can actually react to the roll very easily.
Getting around marth's edgeguarding can be very difficult for new players, but it sounds like he only uses dsmash or something.
There are two ways you can get around it easily:
Sweetspot the ledge (so your upB ends right where the ledge is) is the easiest.
You can also ledgetech, which is important to learn, but very difficult for new players. There are videoguides on youtube (I would link you, but I'm posting from my ipod)
Its also pretty easy to punish marth's smashes once you learn how. Learning to wavedash is REALLY helpful here.
You can:
A) stand near the end and WD back once you see the fsmash start, then run in and grab him.
-or-
B) stand near fsmash range, if you see the animation start, shield and let it hit the shield, then as soon as you can, WD out of your shield towards him and punish accordingly.