Wow, you were dueling at level 5? Now that's what I call a quick start. Ahem...
sjolive is correct: you do NOT want to stay in melee with a rogue. Shaman can melee, but rogues are built for it. At low levels you've got about the same armor (excepting a possible shield), but he has WAY more damage than you.
So don't melee with him and invite disaster. Kite him.
You're too low-level to have access to the shaman's best tool for the purpose: Frost Shock. It's really too bad. Frost Shock is our primary anti-rogue tool, a hard-hitting insta-cast slow spell. The problem is that it's a mana hog, but hopefully you won't have to keep this up for too long. Your other option for kiting is the snare totem, which is your only choice below level 20. It's really too bad, I tend to think that Stoneskin can really help you survive a bit longer... however, the real damage of a rogue is from his specials, not just his straight dagger-damage.
Anyway... if you are at melee range and can't get away, don't let him target you cleanly. Run in random directions! Some of his abilities have specific facing requirements, and confusing him can keep him hesitant. Keep up a steady barrage of shocks and try to keep the damage you take to a minimum. If you have the chance to prepare, strap on a shield instead of a two-hander; Lightning Shield also helps if he should manage to close with you.