The Romans probably weren't aware of either. Iceland wasn't discovered until sometime around the 9th century AD by Norse sailors. Svalbard was discovered much later, by William Barents in 1595.

Sources: http://svalbardmuseum.no/en/kultur-og-historie/oppdagelsen/ http://naturalhistory.si.edu/vikings/voyage/subset/iceland/history.html

On the topic of Scotland being the end of the world you should look into Agricola, an account by Tacitus about his titular father in law. It features a speech by Calgacus, the leader of the Caledonian forces at the Battle of Mons Graupius.

In the speech Calgacus supposedly states:

• "Now, however, the furthest limits of Britain are thrown open, and the unknown always passes for the marvellous. But there are no tribes beyond us, nothing indeed but waves and rocks, and the yet more terrible Romans, from whose oppression escape is vainly sought by obedience and submission."

From this we can take that Calgacus believes Scotland to be the furthest you can run from Rome, in essence the end of the world as you mention. Of course this reflects Tacitus' opinion as its incredibly likely that the speech is a creation on Tacitus' part of putting words into the mouth of what he regarded as these 'noble savages'.

Forgetting the noble savage reasoning behind the speech from this we can assume therefore that Tacitus at least believed Scotland to be the end of the world when he was writing around 100AD. However keep in mind Tacitus was a senator and therefore had access to a wide range of sources and accounts from which he could write his own, meaning that his view probably reflects the view of the Roman Empire at the time in regards to its north-western borders.

Hope this clears up a bit what you were looking for!

We do not really know how early Iceland was discovered. It began to be settled in the late 9th century, and in the Book of Settlements the discovery is placed shortly before that. But it is quite likely it was discovered earlier without us having any written sources thereof. There are at least some archealogy sites in Iceland which raise the possibility that before the settlement there was a period where people hunted in Iceland during the summer.