History of the Vikings

Bjorn Ironside
857 Bjorn in France
 Attacks Paris, leaves only four churches standing. Paris destroyed He and Hastein decide to visit Rome, the start of a four year European tour which also a visit to North Africa and ends in Ireland
The 62 ships route:
Seine to Brittany
Bay of Biscay, frequently stopping and raiding as they go, then onto Spain
Spain their ships laden with silver and gold, they lost two ships in
Guadalquivir, so they avoided Seville.
Straites of Gibralter
Algeciras raided. Then to North Africa
North Africa Where they bought slaves, a whole captured tribe and an Irish monk who was also enslaved as he'd been kidnapped along the tribe he was trying to convert (with quite success it would seem). 
The Balearics, then Narbonne and into the Camargue, sailing up the Rhone as far as Venice
Venice, here they were beaten back
Cote D'Azure 
Ligurarian Riviera (North of Italy)
It is possible they sacked Pisa on the way too
St Quentin
 Here Dudo (chief there) sent messagers as they had heard that Hastein was asking to be baptised as he said he was terminaly ill. Dudo granted this plea, and sent messengers who 
Hastein was then Baptised and given the Chistam name Alstignus, and then died overnight.

The Seine 20 ships remaining.
 
 

Now, they had lost a few ships already, I only have the two reported in the book so far, but even if they still had 60, it is not enough to sack Rome.
 They Might have reached Rome itself, as Hastein feigned illness and sent messages to  St Quenten, Dudo, and had died overnight. Not quite sur where he died as yet, I'll have to hunt further afield

 It is said that a crafty Roman, knowing of their destination, and intent, they were met, told that Rome had already fallen and were taken to an old unused Roman city, called Luna, which included an ampitheatre, to show as proof, There is no proof to show this and Luna, or Lini was excevated in the late 1970s, and not  shred of evidence, No sheilds, no helmets, nothing, not even a spear tip of Viking origin!

Source: Vikings by BBC host of Mastermind, Magnus Magnusson